. Find the radian measure of the largest angle of the triangle whose sides have lengths 8, 9, and 10.

Trigonometry (11th Edition)
11th Edition
ISBN:9780134217437
Author:Margaret L. Lial, John Hornsby, David I. Schneider, Callie Daniels
Publisher:Margaret L. Lial, John Hornsby, David I. Schneider, Callie Daniels
Chapter1: Trigonometric Functions
Section: Chapter Questions
Problem 1RE: 1. Give the measures of the complement and the supplement of an angle measuring 35°.
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**Problem 5:**

Find the radian measure of the largest angle of the triangle whose sides have lengths 8, 9, and 10.

**Explanation:**

To solve this problem, we need to use the Law of Cosines, which relates the lengths of the sides of a triangle to the cosine of one of its angles. The law is expressed as:

\[ c^2 = a^2 + b^2 - 2ab \cdot \cos(C) \]

In this triangle, let the side with length 10 be \( c \), the largest side, and the opposite angle be \( C \). This makes \( a = 8 \) and \( b = 9 \).

Plug these values into the Law of Cosines to find \( \cos(C) \):

\[ 10^2 = 8^2 + 9^2 - 2 \cdot 8 \cdot 9 \cdot \cos(C) \]

\[ 100 = 64 + 81 - 144 \cdot \cos(C) \]

\[ 100 = 145 - 144 \cdot \cos(C) \]

\[ 144 \cdot \cos(C) = 145 - 100 \]

\[ 144 \cdot \cos(C) = 45 \]

\[ \cos(C) = \frac{45}{144} \]

\[ \cos(C) = \frac{5}{16} \]

Now, find \( C \) by taking the arccosine of \(\frac{5}{16}\):

\[ C = \arccos\left(\frac{5}{16}\right) \]

Finally, this calculation will yield the radian measure of the angle \( C \), the largest angle in the triangle.
Transcribed Image Text:**Problem 5:** Find the radian measure of the largest angle of the triangle whose sides have lengths 8, 9, and 10. **Explanation:** To solve this problem, we need to use the Law of Cosines, which relates the lengths of the sides of a triangle to the cosine of one of its angles. The law is expressed as: \[ c^2 = a^2 + b^2 - 2ab \cdot \cos(C) \] In this triangle, let the side with length 10 be \( c \), the largest side, and the opposite angle be \( C \). This makes \( a = 8 \) and \( b = 9 \). Plug these values into the Law of Cosines to find \( \cos(C) \): \[ 10^2 = 8^2 + 9^2 - 2 \cdot 8 \cdot 9 \cdot \cos(C) \] \[ 100 = 64 + 81 - 144 \cdot \cos(C) \] \[ 100 = 145 - 144 \cdot \cos(C) \] \[ 144 \cdot \cos(C) = 145 - 100 \] \[ 144 \cdot \cos(C) = 45 \] \[ \cos(C) = \frac{45}{144} \] \[ \cos(C) = \frac{5}{16} \] Now, find \( C \) by taking the arccosine of \(\frac{5}{16}\): \[ C = \arccos\left(\frac{5}{16}\right) \] Finally, this calculation will yield the radian measure of the angle \( C \), the largest angle in the triangle.
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