Geometry Basics: Angles and Triangles

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Questions and Answers

What does one complete revolution equal?

  • 180 degrees
  • 90 degrees
  • 360 degrees (correct)
  • 270 degrees

What are the degrees of an acute angle?

less than 90 degrees

What are the degrees of a right angle?

90 degrees

What are the degrees of an obtuse angle?

<p>greater than 90 degrees</p> Signup and view all the answers

What are the degrees of a straight angle?

<p>180 degrees</p> Signup and view all the answers

If two angles have a sum of 90 degrees, what are they called?

<p>complementary angles</p> Signup and view all the answers

If two angles have a sum of 180 degrees, what are they called?

<p>supplementary angles</p> Signup and view all the answers

What is the equation for the complementary angle?

<p>90 - y</p> Signup and view all the answers

What is the equation for the supplementary angle?

<p>180 - y</p> Signup and view all the answers

What does a little line (tick) mean if it's going through a line of a triangle?

<p>indicates sides are different in length</p> Signup and view all the answers

Where are the legs a, b, hypotenuse c, and theta located in a right triangle?

<p>a is bottom, b is left, c is longest side, theta is inside</p> Signup and view all the answers

What is the equation for the Pythagorean theorem?

<p>a^2 + b^2 = c^2</p> Signup and view all the answers

What are the degrees for a special triangle that has equal sides?

<p>30 degrees, 60 degrees, 90 degrees</p> Signup and view all the answers

What is the ratio of a 30-60-90 triangle?

<p>t : sqrt(3) * t : 2 * t</p> Signup and view all the answers

What are the two types of special triangles in degrees?

<p>30-60-90 and 45-45-90</p> Signup and view all the answers

What is the ratio for a 45-45-90 degree triangle?

<p>t : t : sqrt(2) * t</p> Signup and view all the answers

What is the vertex of a square?

<p>the common point</p> Signup and view all the answers

Where are the first, second, third, and fourth quadrants located on a graph?

<p>Bottom left- Negative x, Negative y (A), Top right- Positive x, Positive y (B), Bottom right- Positive x, Negative y (C), Top left- Negative x, Positive y (D)</p> Signup and view all the answers

What is the distance formula?

<p>sqrt((x2 - x1)^2 + (y2 - y1)^2)</p> Signup and view all the answers

What letters signify the center point and what letter signifies the radius when finding the equation of a circle?

<p>(h,k) and r</p> Signup and view all the answers

What are the trigonometric functions?

<p>All of the above (D)</p> Signup and view all the answers

What formula do we use to find the remaining trigonometric functions?

<p>r^2 = x^2 + y^2</p> Signup and view all the answers

The reciprocal identities include 1/cosθ = secθ.

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

What are the ratio identities?

<p>cotθ = x/y = cosθ/sinθ, tanθ = sinθ/cosθ</p> Signup and view all the answers

What is the rule to memorize the signs of trigonometric functions in a given quadrant?

<p>CAST rule</p> Signup and view all the answers

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Study Notes

Basic Angle Measurements

  • One complete revolution is 360 degrees.
  • Acute angles measure less than 90 degrees.
  • Right angles measure exactly 90 degrees.
  • Obtuse angles measure greater than 90 degrees but less than 180 degrees.
  • Straight angles measure 180 degrees.

Angle Relationships

  • Complementary angles sum up to 90 degrees.
  • Supplementary angles sum up to 180 degrees.
  • Complementary and supplementary formulas: 90 - y and 180 - y respectively.

Triangle Properties

  • Tick marks on triangle sides indicate length differences (one tick means equal length, different ticks indicate varied lengths).
  • In a right triangle:
    • Hypotenuse (c) is the longest side.
    • Leg a is the bottom side, leg b is the left side.
    • Theta (θ) is located at the angle inside the triangle.

Pythagorean Theorem

  • The formula is a² + b² = c², where c is the hypotenuse.

Special Triangles

  • Equilateral triangles have three equal sides and angles: 60°, 60°, 60°.
  • A 30-60-90 triangle has angles of 30°, 60°, and 90° with side ratios t : √3t : 2t.
  • A 45-45-90 triangle has angles of 45°, 45°, and 90° with side ratios t : t : √2t.

Graphing Coordinates

  • First Quadrant (top right): x and y are positive.
  • Second Quadrant (top left): x is negative, y is positive.
  • Third Quadrant (bottom left): x and y are negative.
  • Fourth Quadrant (bottom right): x is positive, y is negative.

Distance and Circle Formulas

  • Distance formula: √[(x₂ - x₁)² + (y₂ - y₁)²].
  • Circle equation center is at (h,k) with radius r: (x - h)² + (y - k)² = r².

Trigonometric Functions

  • Sine: sin(θ) = y/r
  • Cosine: cos(θ) = x/r
  • Tangent: tan(θ) = y/x
  • Secant: sec(θ) = r/x
  • Cosecant: csc(θ) = r/y
  • Cotangent: cot(θ) = x/y.

Finding Trigonometric Functions

  • To find remaining trig functions, use r² = x² + y² (derived from the Pythagorean theorem).

Identities in Trigonometry

  • Reciprocal identities:
    • cscθ = 1/sinθ
    • secθ = 1/cosθ
    • cotθ = 1/tanθ
  • Ratio identities:
    • cotθ = x/y = cosθ/sinθ
    • tanθ = sinθ/cosθ.

CAST Rule

  • Used to memorize signs of trigonometric functions in different quadrants:
    • C (cos) in the fourth quadrant is positive.
    • A (All) in the first quadrant means all functions are positive.
    • S (sin) in the second quadrant is positive.
    • T (tan) in the third quadrant is positive.

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