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Questions and Answers

If $\triangle ABC \sim \triangle DEF$ and $\frac{AB}{DE} = \frac{2}{3}$, what is the ratio of $\frac{BC}{EF}$?

  • $\frac{3}{2}$
  • $\frac{2}{3}$ (correct)
  • $\frac{9}{4}$
  • $\frac{4}{9}$

Which of the following statements is true regarding similar triangles?

  • The areas of the triangles are equal.
  • Corresponding angles are proportional.
  • Corresponding sides are proportional, and corresponding angles are equal. (correct)
  • Corresponding sides are equal in length.

In a right-angled triangle, what is the ratio that defines the sine of an angle $\theta$?

  • $\frac{\text{adjacent}}{\text{hypotenuse}}$
  • $\frac{\text{opposite}}{\text{adjacent}}$
  • $\frac{\text{adjacent}}{\text{opposite}}$
  • $\frac{\text{opposite}}{\text{hypotenuse}}$ (correct)

Which trigonometric ratio is the reciprocal of $\sin \theta$?

<p>$\text{cosec } \theta$ (A)</p> Signup and view all the answers

What is the value of $\cos 60^\circ$?

<p>$\frac{1}{2}$ (A)</p> Signup and view all the answers

In a right triangle, if the opposite side to an angle $\theta$ is 5 and the hypotenuse is 13, what is $\sin \theta$?

<p>$\frac{5}{13}$ (A)</p> Signup and view all the answers

If $\tan \theta = 1$ and $0^\circ < \theta < 90^\circ$, what is the measure of angle $\theta$?

<p>$45^\circ$ (C)</p> Signup and view all the answers

What is the value of $\sin 30^\circ + \cos 60^\circ$?

<p>1 (A)</p> Signup and view all the answers

In the Cartesian plane, an angle $\theta$ has its terminal arm in Quadrant II. Which trigonometric ratio is positive in this quadrant?

<p>$\sin \theta$ (C)</p> Signup and view all the answers

An observer looks up at a bird at an angle of elevation of $30^\circ$. If the bird is 10 meters above the observer's horizontal line of sight, what is the horizontal distance between the observer and the bird?

<p>$10\sqrt{3}$ meters (C)</p> Signup and view all the answers

If $\cos \theta = \frac{1}{3}$, find the value of $\sin^2 \theta + \cos^2 \theta$.

<p>1 (A)</p> Signup and view all the answers

Given $\triangle ABC$ is a right-angled triangle with $\angle C = 90^\circ$, $AB = 10$, and $BC = 5$, find the value of $\tan A$.

<p>$\frac{\sqrt{3}}{3}$ (A)</p> Signup and view all the answers

If $\sin \theta = \frac{3}{5}$ and $\theta$ is in the second quadrant, what is the value of $\cos \theta$?

<p>$\frac{-4}{5}$ (B)</p> Signup and view all the answers

A ladder leans against a wall, making an angle of $60^\circ$ with the ground. The foot of the ladder is 2 meters away from the wall. How far up the wall does the ladder reach?

<p>$2\sqrt{3}$ meters (C)</p> Signup and view all the answers

What is the exact value of$\sin(22.5^\circ)$?

<p>$\frac{\sqrt{2 - \sqrt{2}}}{2}$ (D)</p> Signup and view all the answers

Two similar triangles, $\triangle ABC$ and $\triangle DEF$, have areas of $16 \text{ cm}^2$ and $25 \text{ cm}^2$ respectively. If $AB = 4 \text{ cm}$, what is the length of $DE$?

<p>5 cm (B)</p> Signup and view all the answers

Given that $\cos(x) = \frac{1}{7}$ and $\cos(y) = \frac{13}{14}$, where $x$ and $y$ are acute angles, what is the value of $\cos(x - y)$?

<p>$\frac{\sqrt{3}}{2}$ (D)</p> Signup and view all the answers

Determine the number of solutions to the equation $\sin(x) = \frac{x}{100}$

<p>63 (D)</p> Signup and view all the answers

Consider a triangle in the Cartesian plane with vertices at (0, 0), (5, 0), and (0, 12). What is the sine of the angle at the origin?

<p>$\frac{12}{13}$ (D)</p> Signup and view all the answers

A tower casts a shadow of 30 meters when the angle of elevation of the sun is 60°. What is the height of the tower?

<p>$30\sqrt{3}$ meters (B)</p> Signup and view all the answers

In a $30^\circ$-$60^\circ$-$90^\circ$ triangle, what is the ratio of the side opposite to $30^\circ$ to the hypotenuse?

<p>$1:2$ (D)</p> Signup and view all the answers

In which quadrant of the Cartesian plane is $ an heta$ positive and $\cos heta$ negative?

<p>Quadrant III (A)</p> Signup and view all the answers

Consider two similar triangles $ riangle ABC$ and $ riangle DEF$. If the ratio of their corresponding heights is $3:5$, what is the ratio of their areas?

<p>$9:25$ (A)</p> Signup and view all the answers

If in $ riangle ABC$ and $ riangle DEF$, $\angle A = \angle D$ and $\angle B = \angle E$, and $AB = 2DE$, what is the ratio of the area of $ riangle ABC$ to the area of $ riangle DEF$?

<p>$4:1$ (B)</p> Signup and view all the answers

Given that $\sin x = \cos y$ for acute angles $x$ and $y$, what can be concluded about the relationship between $x$ and $y$?

<p>$x + y = 90^\circ$ (A)</p> Signup and view all the answers

If two triangles are similar, which of the following statements about their corresponding angles is always true?

<p>They are equal. (C)</p> Signup and view all the answers

In a right-angled triangle $ABC$, where $C$ is the right angle, which side is the hypotenuse?

<p>The side opposite angle C. (A)</p> Signup and view all the answers

What is the relationship between $an heta$ and $\cot heta$?

<p>They are reciprocals of each other. (A)</p> Signup and view all the answers

In which quadrant of the Cartesian plane are both sine and cosine negative?

<p>Quadrant III (C)</p> Signup and view all the answers

A surveyor measures the angle of elevation to the top of a building to be $25^\circ$. If the surveyor is standing 50 meters from the base of the building, approximately how tall is the building?

<p>23.32 meters (D)</p> Signup and view all the answers

Given that $ext{cosec } heta = 2$, what is the value of $\sin heta$?

<p>0.5 (D)</p> Signup and view all the answers

What is the value of $\sin^2(45^\circ) + \cos^2(45^\circ)$?

<p>1 (C)</p> Signup and view all the answers

If a right triangle has legs of length 3 and 4, what is the cosine of the angle opposite the side of length 3?

<p>$4/5$ (D)</p> Signup and view all the answers

Two buildings are 50 meters apart. The angle of depression from the top of the taller building to the top of the shorter building is $20^\circ$. If the taller building is 70 meters tall, how tall is the shorter building?

<p>52.8 meters (D)</p> Signup and view all the answers

Given a triangle $ABC$ with sides $a$, $b$, and $c$ opposite to angles $A$, $B$, and $C$ respectively, and given that $a = 10$, $b = 12$, and $C = 60^\circ$, find the length of side $c$.

<p>$c = \sqrt{148}$ (D)</p> Signup and view all the answers

If $ \triangle PQR \sim \triangle XYZ $ and $ \frac{PQ}{XY} = \frac{5}{7} $, what is the value of $ \frac{PR}{XZ} $?

<p>$ \frac{5}{7} $ (B)</p> Signup and view all the answers

In a right triangle, which trigonometric ratio represents the relationship between the adjacent side and the hypotenuse?

<p>$ \cos \theta $ (D)</p> Signup and view all the answers

If $ \tan(\theta) = \frac{4}{3} $, what is the value of $ \cot(\theta) $?

<p>$ \frac{3}{4} $ (D)</p> Signup and view all the answers

Given $ \triangle ABC \sim \triangle MNP $, which of the following statements must be true?

<p>$ \angle A = \angle M $ (A)</p> Signup and view all the answers

In a right triangle $ ABC $ with right angle at $ C $, if $ AB = 13 $ and $ BC = 5 $, find $ \cos A $.

<p>$ \frac{12}{13} $ (B)</p> Signup and view all the answers

If an angle $ \theta $ in the Cartesian plane has its terminal arm in Quadrant III, which of the following is true?

<p>$ \sin \theta &lt; 0 $ and $ \cos \theta &lt; 0 $ (D)</p> Signup and view all the answers

A ladder 6 meters long leans against a wall, making an angle of 75° with the ground. How high up the wall does the ladder reach?

<p>$ 6 \sin 75^\circ $ (C)</p> Signup and view all the answers

Given that $ \sin \theta = \frac{1}{2} $ and $ 0^\circ < \theta < 90^\circ $, what is the value of $ \cos \theta $?

<p>$ \frac{\sqrt{3}}{2} $ (D)</p> Signup and view all the answers

If $ \cos(\theta) = \frac{5}{13} $ and $ \theta $ is in the fourth quadrant, what is $ \tan(\theta) $?

<p>$ -\frac{12}{5} $ (A)</p> Signup and view all the answers

An observer stands 50 meters away from a building and observes the top of the building at an angle of elevation of $30^\circ$. What is the height of the building?

<p>$ \frac{50}{\sqrt{3}} $ meters (C)</p> Signup and view all the answers

What is the exact value of $ \cos 15^\circ $?

<p>$ \frac{\sqrt{6} + \sqrt{2}}{4} $ (A)</p> Signup and view all the answers

Given $ \sin x = \frac{1}{\sqrt{5}} $ and $ \cos y = \frac{2}{\sqrt{5}} $, where both $ x $ and $ y $ are acute angles, find the value of $ \sin(x + y) $.

<p>1 (C)</p> Signup and view all the answers

In triangle $ ABC $, $ a = 5 $, $ b = 7 $, and $ \angle C = 60^\circ $. Find the length of side $ c $.

<p>$ \sqrt{39} $ (D)</p> Signup and view all the answers

What is the range of the function $ f(x) = 3 \sin(2x) + 1 $?

<p>$\lbrack -2, 4 \rbrack$ (D)</p> Signup and view all the answers

Consider the function $ f(x) = \frac{\sin x}{x} $ for $ x > 0 $. What value does $ f(x) $ approach as $ x $ approaches infinity?

<p>0 (A)</p> Signup and view all the answers

Find the exact value of $ \tan(\frac{5\pi}{12}) $.

<p>$ 2 + \sqrt{3} $ (B)</p> Signup and view all the answers

Given a regular hexagon inscribed in a circle of radius 1, what is the value of the product of the distances from one vertex to all other vertices?

<p>6 (D)</p> Signup and view all the answers

Flashcards

Similar Triangles

Triangles with equal angles have proportional corresponding sides, regardless of size.

Properties of Similar Triangles

For similar triangles $ \Delta ABC \sim \Delta DEF $, corresponding angles are equal, and $ \frac{AB}{DE} = \frac{BC}{EF} = \frac{AC}{DF} $.

Sides of a Right Triangle

In a right triangle relative to angle $ \theta $, the hypotenuse is opposite the right angle, the opposite is across from $ \theta $, and the adjacent is next to $ \theta $.

Trigonometric Ratios

$ \sin \theta = \frac{\text{opposite}}{\text{hypotenuse}} $, $ \cos \theta = \frac{\text{adjacent}}{\text{hypotenuse}} $, $ \tan \theta = \frac{\text{opposite}}{\text{adjacent}} $.

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Reciprocal Trigonometric Ratios

$ \csc \theta = \frac{1}{\sin \theta} $, $ \sec \theta = \frac{1}{\cos \theta} $, $ \cot \theta = \frac{1}{\tan \theta} $

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30-60-90 Triangle Ratios

In a 30-60-90 triangle, sides are in the ratio 1:$ \sqrt{3}$:2; Opposite 30°: 1, Opposite 60°: $ \sqrt{3} $, Hypotenuse: 2.

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45-45-90 Triangle Ratios

In a 45-45-90 triangle, the sides are in the ratio 1:1:$ \sqrt{2} $; Each leg (opposite 45°): 1, Hypotenuse: $ \sqrt{2} $.

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Trigonometric Ratios for 30°

$ \sin 30^\circ = \frac{1}{2} $, $ \cos 30^\circ = \frac{\sqrt{3}}{2} $, $ \tan 30^\circ = \frac{\sqrt{3}}{3} $

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Trigonometric Ratios for 45°

$ \sin 45^\circ = \frac{\sqrt{2}}{2} $, $ \cos 45^\circ = \frac{\sqrt{2}}{2} $, $ \tan 45^\circ = 1 $

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Trigonometric Ratios for 60°

$ \sin 60^\circ = \frac{\sqrt{3}}{2} $, $ \cos 60^\circ = \frac{1}{2} $, $ \tan 60^\circ = \sqrt{3} $

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Finding Angles

Use inverse trigonometric functions to find unknown angles when two sides are known; $ \theta = \sin^{-1}(\frac{\text{opposite}}{\text{hypotenuse}}) $, $ \theta = \cos^{-1}(\frac{\text{adjacent}}{\text{hypotenuse}}) $, $ \theta = \tan^{-1}(\frac{\text{opposite}}{\text{adjacent}}) $.

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Trig Ratios in Cartesian Plane

Trigonometric ratios in the Cartesian plane: $ \sin \theta = \frac{y}{r} $, $ \cos \theta = \frac{x}{r} $, $ \tan \theta = \frac{y}{x} $, where $ r = \sqrt{x^2 + y^2} $.

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CAST Diagram

CAST diagram indicates signs of trigonometric functions in each quadrant: All, Sine, Tan, Cosine are positive in Quadrants I, II, III, IV respectively.

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Angle of Elevation

Angle above the horizontal when looking up.

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Angle of Depression

Angle below the horizontal when looking down.

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Sine (sin)

In trigonometry, this ratio relates the opposite side to the hypotenuse in a right triangle.

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Cosine (cos)

In trigonometry, this ratio relates the adjacent side to the hypotenuse in a right triangle.

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Tangent (tan)

In trigonometry, this ratio relates the opposite side to the adjacent side in a right triangle.

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Reciprocal Trig Functions

The reciprocals of sine, cosine, and tangent.

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Tangent in terms of sine and cosine

The ratio of sine to cosine.

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Mnemonic Device for CAST Diagram

A diagram used to remember which trigonometric functions are positive in each quadrant of the Cartesian plane.

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Trigonometric Ratios in All Quadrants

These ratios extend the definitions of sine, cosine, and tangent to all angles.

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Solving for Side Lengths

Finding unknown side lengths in right triangles using trigonometric ratios.

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Ratios of Similar Triangles

The relationship between sides of similar triangles

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Cosecant

The trigonometric ratio that is equivalent to $ \frac{\text{hypotenuse}}{\text{opposite}} $

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Secant

The trigonometric ratio that is equivalent to $ \frac{\text{hypotenuse}}{\text{adjacent}} $

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Cotangent

The trigonometric ratio that is equivalent to $ \frac{\text{adjacent}}{\text{opposite}} $

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Key Ratios of Similar Triangles

If $ \Delta ABC \sim \Delta DEF \sim \Delta GHK $, then $ \frac{AB}{BC} = \frac{DE}{EF} = \frac{GH}{HK} $, $ \frac{AB}{AC} = \frac{DE}{DF} = \frac{GH}{GK} $, and $ \frac{BC}{AC} = \frac{EF}{DF} = \frac{HK}{GK} $.

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Soh Cah Toa

A memory aid for trigonometric ratios: $ \sin = \frac{\text{opposite}}{\text{hypotenuse}} $, $ \cos = \frac{\text{adjacent}}{\text{hypotenuse}} $, $ \tan = \frac{\text{opposite}}{\text{adjacent}} $.

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Reciprocal Relationships

Relationship between a trigonometric function and its reciprocal.

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Finding Lengths with Trig Ratios

Using trigonometric ratios to find a side length when an angle and another side are known.

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Solve for opposite side

If $ \sin \theta = \frac{\text{opposite}}{\text{hypotenuse}} $, then $ \text{opposite} = \text{hypotenuse} \times \sin \theta $.

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Quadrant I

In Quadrant I (0°–90°), All trigonometric functions are positive.

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Quadrant II

In Quadrant II (90°–180°), $ \sin $ and $ \text{cosec} $ are positive.

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Quadrant III

In Quadrant III (180°–270°), $ \tan $ and $ \cot $ are positive.

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Quadrant IV

In Quadrant IV (270°–360°), $ \cos $ and $ \sec $ are positive.

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Applications of Trigonometry

Trigonometry can be applied to solve problems involving right-angled triangles in fields like construction and navigation.

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Elevation vs. Depression

The angle of elevation from one point equals the angle of depression from the corresponding point.

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Study Notes

  • Grade 10 trigonometry involves understanding similar triangles, trigonometric ratios, special angles, solving trigonometric equations, trigonometric ratios in the Cartesian plane, and two-dimensional problems.

Similarity of Triangles

  • Similarity of triangles is foundational to understanding trigonometry.
  • In similar triangles, the ratios of corresponding sides are proportional if the angles are equal.

Ratios of Similar Triangles

  • For similar triangles $\Delta ABC$, $\Delta DEF$, and $\Delta GHK$, the ratios of corresponding sides are equal:
    • $\frac{AB}{BC} = \frac{DE}{EF} = \frac{GH}{HK}$
    • $\frac{AB}{AC} = \frac{DE}{DF} = \frac{GH}{GK}$
    • $\frac{BC}{AC} = \frac{EF}{DF} = \frac{HK}{GK}$
  • For $\Delta ABC \sim \Delta DEF$, the ratios of corresponding sides are equal
    • $\frac{AB}{DE} = \frac{BC}{EF} = \frac{AC}{DF}$
  • Corresponding angles in similar triangles are equal:
    • $\angle A = \angle D$
    • $\angle B = \angle E$
    • $\angle C = \angle F$
  • Ratios of corresponding sides in similar triangles are equal.
  • If the angle remains constant, the ratio remains constant.

Trigonometric Ratios

  • Trigonometric ratios are defined using similar right-angled triangles.
  • Consider $\triangle ABC$ with a right angle at $C$ and an angle $\theta$ at $A$.

Defining the Trigonometric Ratios

  • In relation to $\theta$:
    • Hypotenuse: side opposite the right angle.
    • Opposite: side opposite $\theta$.
    • Adjacent: side next to $\theta$.
  • The formulas for the main trigonometric ratios are:
    • $\sin \theta = \frac{\text{opposite}}{\text{hypotenuse}}$
    • $\cos \theta = \frac{\text{adjacent}}{\text{hypotenuse}}$
    • $\tan \theta = \frac{\text{opposite}}{\text{adjacent}}$
  • Mnemonic (Soh Cah Toa):
    • $\sin \theta = \frac{\text{opposite}}{\text{hypotenuse}}$ (Soh)
    • $\cos \theta = \frac{\text{adjacent}}{\text{hypotenuse}}$ (Cah)
    • $\tan \theta = \frac{\text{opposite}}{\text{adjacent}}$ (Toa)

Reciprocal Ratios

  • Each trigonometric ratio has a reciprocal:
    • $\text{cosec } \theta = \frac{1}{\sin \theta} = \frac{\text{hypotenuse}}{\text{opposite}}$
    • $\text{sec } \theta = \frac{1}{\cos \theta} = \frac{\text{hypotenuse}}{\text{adjacent}}$
    • $\text{cot } \theta = \frac{1}{\tan \theta} = \frac{\text{adjacent}}{\text{opposite}}$
  • The relationships between trigonometric ratios and their reciprocals are:
    • $\sin \theta \times \text{cosec } \theta = 1$
    • $\cos \theta \times \text{sec } \theta = 1$
    • $\tan \theta \times \text{cot } \theta = 1$

Special Angles

  • Special angles produce simple trigonometric ratios without a calculator.

Special Angle Triangles

  • 30°-60°-90° Triangle:
    • Hypotenuse: 2
    • Opposite 30°: 1
    • Opposite 60°: $\sqrt{3}$
  • 45°-45°-90° Triangle:
    • Hypotenuse: $\sqrt{2}$
    • Each leg (opposite 45°): 1

Trigonometric Ratios for Special Angles

  • The trigonometric ratios for the special angles are:
    • $\sin 30^\circ = \frac{1}{2}$, $\cos 30^\circ = \frac{\sqrt{3}}{2}$, $\tan 30^\circ = \frac{\sqrt{3}}{3}$
    • $\sin 45^\circ = \frac{\sqrt{2}}{2}$, $\cos 45^\circ = \frac{\sqrt{2}}{2}$, $\tan 45^\circ = 1$
    • $\sin 60^\circ = \frac{\sqrt{3}}{2}$, $\cos 60^\circ = \frac{1}{2}$, $\tan 60^\circ = \sqrt{3}$

Solving Trigonometric Equations

Finding Lengths

  • Using trigonometric ratios, unknown side lengths in right-angled triangles can be determined when one angle and one side are known.
  • To solve for the opposite side:
    • $\text{opposite} = \text{hypotenuse} \times \sin \theta$

Finding Angles

  • When two sides are known, angles can be found using inverse trigonometric functions:
    • $\theta = \sin^{-1}\left(\frac{\text{opposite}}{\text{hypotenuse}}\right)$
    • $\theta = \cos^{-1}\left(\frac{\text{adjacent}}{\text{hypotenuse}}\right)$
    • $\theta = \tan^{-1}\left(\frac{\text{opposite}}{\text{adjacent}}\right)$
  • Steps to solve for an unknown angle:
    • Identify the trigonometric ratio.
    • Rearrange to isolate the ratio.
    • Use a calculator to find the angle via inverse functions.

Trigonometric Ratios in the Cartesian Plane

Defining Ratios

  • Trigonometric ratios extend to any angle in the Cartesian plane using coordinates $(x, y)$ and radius $r = \sqrt{x^2 + y^2}$:
    • $\sin \theta = \frac{y}{r}$, $\cos \theta = \frac{x}{r}$, $\tan \theta = \frac{y}{x}$
    • $\text{cosec } \theta = \frac{r}{y}$, $\text{sec } \theta = \frac{r}{x}$, $\text{cot } \theta = \frac{x}{y}$

CAST Diagram

  • The CAST diagram defines signs of trigonometric functions in each quadrant:
    • Quadrant I (0°–90°): All positive
    • Quadrant II (90°–180°): $\sin$ and $\text{cosec}$ positive
    • Quadrant III (180°–270°): $\tan$ and $\cot$ positive
    • Quadrant IV (270°–360°): $\cos$ and $\sec$ positive

Special Angles in the Cartesian Plane

  • The trigonometric ratios for the special angles are:
    • $\sin 0^\circ = 0$, $\cos 0^\circ = 1$, $\tan 0^\circ = 0$
    • $\sin 90^\circ = 1$, $\cos 90^\circ = 0$, $\tan 90^\circ = \text{undefined}$

Two-Dimensional Problems

Applications

  • Trigonometry is used to solve practical problems involving right-angled triangles, such as construction and navigation.
  • Angle of Elevation:
    • The angle above the horizontal when looking up at an object.
  • Angle of Depression:
    • The angle below the horizontal when looking down at an object.
  • The angle of elevation from one point equals the angle of depression from the corresponding point.

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