Triangle Inequality Theorem

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Questions and Answers

Given a triangle with sides measuring 5 cm and 8 cm, which of the following could be the length of the third side, adhering to the Triangle Inequality Theorem?

  • 2 cm
  • 12 cm (correct)
  • 14 cm
  • 3 cm

If two sides of a triangle are 7 inches and 11 inches, which inequality represents all possible lengths, $x$, for the third side?

  • $x > 18$
  • $4 > x > 18$
  • $4 < x < 18$ (correct)
  • $x < 4$

In triangle ABC, AB = 6 cm and BC = 8 cm. What is the range of possible lengths for side AC?

  • $AC < 2$
  • $AC > 14$
  • $2 > AC > 14$
  • $2 < AC < 14$ (correct)

Which of the following sets of side lengths can form a triangle?

<p>5 cm, 7 cm, 10 cm (D)</p> Signup and view all the answers

Can a triangle be formed with sides of the following lengths: 4, 5, and 10?

<p>No, because 4 + 5 &lt; 10 (B)</p> Signup and view all the answers

In $\triangle PQR$, if $PQ = 9$ and $QR = 12$, which of the following could be a possible length for PR?

<p>4 (A)</p> Signup and view all the answers

Two sides of a triangle measure 6 cm and 11 cm. Which measurement could not be the length of the third side?

<p>16 cm (D)</p> Signup and view all the answers

If the sides of a triangle are 3x, 4x, and 5x, what range of values must x have for the triangle to exist?

<p>$x &gt; 0$ (C)</p> Signup and view all the answers

Given $\triangle ABC$ with sides $AB=5$, $BC=6$, and $CA=7$. Which angle has the smallest measure?

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

In $\triangle XYZ$, $XY = 8$, $YZ = 10$, and $XZ = 12$. Which angle has the largest measure?

<p>$\angle Y$ (B)</p> Signup and view all the answers

In triangle $DEF$, if $DE = 15$, $EF = 13$, and $DF = 18$, which angle is the largest?

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

If in $\triangle ABC$, $AB < BC < AC$, then which of the following is true regarding the angles?

<p>$\angle B &lt; \angle C &lt; \angle A$ (D)</p> Signup and view all the answers

Given a triangle where $\angle A = 80^\circ$ and $\angle B = 60^\circ$, which side of the triangle is the longest?

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

In $\triangle PQR$, if $\angle P = 50^\circ$ and $\angle Q = 70^\circ$, which side is the shortest?

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

In $\triangle ABC$, if $m\angle A = 90^\circ$, $m\angle B = 60^\circ$, and $m\angle C = 30^\circ$, which side is the longest?

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

Given $\triangle XYZ$ with $\angle X = 45^\circ$, $\angle Y = 75^\circ$, and $\angle Z = 60^\circ$, arrange the sides in ascending order.

<p>YZ &lt; XZ &lt; XY (C)</p> Signup and view all the answers

Two triangles, $\triangle ABC$ and $\triangle DEF$, have $AB = DE$ and $BC = EF$. If $m\angle B > m\angle E$, which statement is true according to the Hinge Theorem?

<p>$AC &gt; DF$ (A)</p> Signup and view all the answers

In $\triangle PQR$ and $\triangle STU$, $PQ = ST$ and $QR = TU$. If $PR < SU$, what can be concluded about the angles $\angle Q$ and $\angle T$?

<p>$m\angle Q &lt; m\angle T$ (A)</p> Signup and view all the answers

Given $\triangle ABC$ and $\triangle DEF$ where $AB \cong DE$, $BC \cong EF$, and $AC > DF$. Which of the following statements is true?

<p>$m\angle B &gt; m\angle E$ (A)</p> Signup and view all the answers

Two triangles, $\triangle LMN$ and $\triangle PQR$, have sides such that $LM = PQ$ and $MN = QR$. If $\angle M$ measures $70^\circ$ and $\angle Q$ measures $55^\circ$, which of the following is always true?

<p>$LN &gt; PR$ (B)</p> Signup and view all the answers

In $\triangle ABC$, point D is on side AC such that BD bisects $\angle ABC$. If $AB=8$, $BC=10$, then which of the following must be true?

<p>$AD &lt; CD$ (D)</p> Signup and view all the answers

Given that in $\triangle ABC$, $\angle A$ is an obtuse angle, which side is the longest?

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

If $m\angle 1 = 130^\circ$ is an exterior angle of a triangle, what can you conclude about the measures of the two non-adjacent interior angles?

<p>Both angles must be acute. (A)</p> Signup and view all the answers

In a triangle, if one exterior angle measures $120^\circ$, what is the largest possible measure of one of the remote interior angles?

<p>$119^\circ$ (A)</p> Signup and view all the answers

Considering the Exterior Angle Inequality Theorem, which statement is always true about an exterior angle of a triangle?

<p>It is equal to the sum of the two non-adjacent interior angles. (B)</p> Signup and view all the answers

Given $\triangle ABC$, where D is a point on BC such that AD is not an altitude. If $\angle ADB$ is obtuse, then...

<p>AB &lt; AC (C)</p> Signup and view all the answers

In quadrilateral ABCD, diagonals AC and BD intersect at point E. If $AB = BC$ and $\angle AEB > \angle BEC$, then:

<p>$AD &gt; CD$ (D)</p> Signup and view all the answers

In $\triangle ABC$, point $D$ lies on $BC$ such that $AD$ bisects $\angle BAC$. If $AB = 10$ and $AC = 15$, what can be said about the lengths of $BD$ and $DC$?

<p>$BD &lt; DC$ (D)</p> Signup and view all the answers

If in $\triangle ABC$, $D$ is a point on $BC$ such that $AD \perp BC$. Which of the following is always true?

<p>None of the above (D)</p> Signup and view all the answers

Given the sides of a triangle are 5, 7 and 8, arrange the angles ($\angle A$, $\angle B$, $\angle C$) from smallest to largest, where $A$ is opposite the side of length 5, $B$ is opposite the side of length 7, and $C$ is opposite the side of length 8.

<p>$\angle A &lt; \angle B &lt; \angle C$ (A)</p> Signup and view all the answers

In triangles $\triangle ABC$ and $\triangle DEF$, $AB=DE$ and $BC=EF$. It is known that $AC > DF$. Which of the following can be concluded?

<p>$\angle B &gt; \angle E$ (A)</p> Signup and view all the answers

Which of the following statements correctly uses the Hinge Theorem?

<p>If two sides of one triangle are congruent to two sides of another triangle, then the triangle with the larger included angle has the longer third side. (C)</p> Signup and view all the answers

If you were to apply triangle inequalities to estimate the distance between three cities, A, B, and C, what real-world assumption must you make to apply the theorem correctly?

<p>The roads connecting the cities are perfectly straight. (B)</p> Signup and view all the answers

In the real world, how might understanding triangle inequalities help ensure the structural integrity of a bridge design?

<p>By calculating the minimum length of support beams needed to withstand specific loads. (B)</p> Signup and view all the answers

A surveyor needs to determine the possible distances between two points across a lake. He knows the distance from his position to each of the points. How can he use the Triangle Inequality Theorem?

<p>He can find the range of possible distances between the two points across the lake. (D)</p> Signup and view all the answers

How does the concept of triangle inequality apply to navigation and route planning?

<p>It helps in finding the shortest distance between two points when direct travel is impossible. (B)</p> Signup and view all the answers

Given a fixed length of fencing material, how does the Triangle Inequality Theorem inform the maximum area you can enclose in a triangular shape?

<p>It suggests that the most equilateral triangle maximizes area. (B)</p> Signup and view all the answers

How could the principles behind the triangle inequality theorem be applied to optimize network routing in computer science?

<p>By finding alternative data paths that, while longer, avoid congested routes. (B)</p> Signup and view all the answers

Consider the design of a suspension bridge. How does understanding triangle inequalities contribute to the stability and safety of the structure?

<p>By calculating the precise angles for the deck's suspension cables, ensuring equal weight distribution. (A)</p> Signup and view all the answers

Imagine you're placing two security cameras to cover a specific area. How might triangle inequalities guide your decision-making?

<p>To ensure blind spots are minimized based on the distances and angles between cameras and key locations. (D)</p> Signup and view all the answers

How can understanding triangle inequalities aid in architectural design, particularly in ensuring the stability of roof structures?

<p>By calculating the optimal angles between roof supports to distribute weight evenly and prevent collapse. (C)</p> Signup and view all the answers

Explain how triangle inequalities could be applied to GPS technology to improve the accuracy of location tracking.

<p>By calculating acceptable error ranges in satellite distance measurements to provide a more reliable location fix. (C)</p> Signup and view all the answers

Flashcards

What is a KWL chart?

A chart used to record what students Know, what they Want to learn, and what they have Learned about a topic.

What is 4 Pics 1 Word?

A game where each level shows four pictures linked by one word that the player has to guess using given letters.

Triangle Inequality Theorem

In a triangle, the sum of the lengths of any two sides must be greater than the length of the third side.

Unequal Sides Theorem

If one side of a triangle is longer than another side, then the angle opposite the longer side is larger than the angle opposite the shorter side.

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Unequal Angles Theorem

If one angle of a triangle is larger than another angle, then the side opposite the larger angle is longer than the side opposite the smaller angle.

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Hinge Theorem

If two triangles have two pairs of congruent sides, then the triangle with the larger included angle has the longer third side.

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Converse of the Hinge Theorem

If two triangles have two pairs of congruent sides, then the triangle with the longer third side has the larger included angle.

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Exterior Angle Inequality Theorem

The measure of an exterior angle of a triangle is equal to the sum of the two remote interior angles.

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Study Notes

Work Plan Overview

  • The work plan involves four stages: explore, firm-up, deepen, and transfer.
  • Stage 1: Explore involves using a KWL chart.
  • Stage 2: Firm-up includes "4 Pics 1 Word" and "Triangle or Not."
  • Stage 3: Deepen involves "Arrange Me!" and "Complete It!"
  • Stage 4: Transfer focuses on proving the theorems.

4 Pics 1 Word

  • Each level presents four pictures linked by a common word.
  • The aim is to identify the word using a set of letters provided.

Triangle Inequalities Theorems

Learning Competency

  • Illustrate theorems on triangle inequalities, including Exterior Angle Inequality Theorem, Triangle Inequality Theorem, and Hinge Theorem (M8GE-IVa-).
  • Apply theorems on triangle inequalities (M8GE-IVb-1).
  • Prove inequalities in a triangle (M8GE-IVc-1).

Triangle Inequality Theorem

  • The sum of the lengths of any two sides of a triangle is greater than the length of the third side.
  • Given triangle ABC: AC + CB > AB, AC + AB > BC, and AB + BC > AC

Triangle Side Length Example

  • Problem: verify if a triangle can be constructed with sides 5 cm, 6 cm, and 7 cm.
  • Solution: 5 cm + 6 cm > 7 cm, 6 cm + 7 cm > 5 cm , and 5 cm + 7 cm > 6 cm, so a triangle can be constructed.
  • Problem: can a triangle be constructed with sides of lengths 3 cm, 9 cm, and 10 cm.
  • Solution: 3 cm + 9 cm > 10 cm is false so a triangle cannot be constructed from those measurements

Triangle Side Length - Range Example

  • In triangle BOS, BO = 8, OS = 10, and BS = x. The range of possible values for BS is:
  • x must be greater than 2 and less than 18, thus 2 < BS < 18.

Triangle or Not

  • Determine if a given set of lengths can form a triangle. Write "T" if it can, or "NT" if it cannot.

Drills

  • Determine if a triangle can be constructed with given side lengths, e.g., 7cm, 10cm, and 13cm.
  • Find the range of possible values for a side, e.g., in ΔMAT, MA = 16, AT = 20, and MT = x, what is the range of possible values for MT?

Unequal Sides Theorem

  • If one side of a triangle is longer than another, the angle opposite the longer side is larger than the angle opposite the shorter side.
  • If BC > AC, then m∠A > m∠B.

Arrange Sides Example

  • Arrange sides in descending order based on their lengths.

Unequal Angles Theorem

  • If one angle of a triangle is larger than another, then the side opposite the larger angle is longer than the side opposite the smaller angle.
  • If m∠A > m∠C, then BC > AB.

Arrange Angles Example

  • Arrange the angles in descending or decreasing order. Given the measures of the angles
  • Solution: From triangle TVS where ∠V =70°, ∠A=60° and ∠T = 50°, then m∠V > m∠A > m∠T

Arrange Me!

  • Arrange the angles or sides in descending order or decreasing order.
  • Arrange the angles or sides in ascending order or increasing order.

Hinge Theorem

  • If two triangles have two sets of congruent sides, the larger included angle will have the longer third side.

Converse of the Hinge Theorem

  • If two triangles have two congruent sides, then the triangle with the longer third side will have a larger angle opposite that third side.

Complete Me!

  • Complete statements using >, <, or = based on given triangle properties.

Exterior Angles Inequality Theorem

  • The measure of an exterior angle of a triangle equals the sum of the two remote interior angles.
  • Exterior Angle = Remote Interior Angle 1 + Remote Interior Angle 2.
  • ∠4 = ∠1 + ∠3, ∠4 > ∠2, and ∠4 > ∠3

Exterior Angles Example

  • Use the Exterior Angles Inequality Theorem and sum of all angles in a triangle to determine the measures of unidentified angles.

Prove It!

  • Using the measures of angles and the side lengths of a triangle, apply theorems to prove if it is a true geometrical statement
  • Given LC ≅ CU and CU ≅ UK and m∠K > m∠1, prove UL > CK

Prove Me True

  • Given LO ≅ LE and VE ≅ VO, prove m∠1 < m∠3.

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