Lau of costnEs Th ARST, r= 3.9 inches,S= S. inches and +=6.1inches. Find the measuKC of LS +to the neavGJA 10th dagsee.

Elementary Geometry For College Students, 7e
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ISBN:9781337614085
Author:Alexander, Daniel C.; Koeberlein, Geralyn M.
Publisher:Alexander, Daniel C.; Koeberlein, Geralyn M.
ChapterP: Preliminary Concepts
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**Trigonometry Problem: Using the Law of Cosines to Find an Angle**

In the given triangle \( \Delta RST \), the side lengths are as follows: \( r = 3.9 \) inches, \( s = 5.6 \) inches, and \( t = 6.1 \) inches.

To find the measure of angle \( \angle S \) to the nearest 10th degree, you can use the Law of Cosines formula:

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

Where \( a \), \( b \), and \( c \) are the sides of the triangle, and \( C \) is the angle opposite side \( c \).

**Step-by-Step Solution:**

1. Identify the sides opposite to the angles:
   - In this case, let side \( r \) be opposite angle \( \angle R \),
   - side \( s \) be opposite angle \( \angle S \),
   - and side \( t \) be opposite angle \( \angle T \).

2. Rewrite the Law of Cosines for finding \( \angle S \):
   \[ s^2 = r^2 + t^2 - 2rt \cdot \cos(S) \]

3. Substitute the known values:
   \[ 5.6^2 = 3.9^2 + 6.1^2 - 2 \cdot 3.9 \cdot 6.1 \cdot \cos(S) \]

4. Calculate each term:
   \[ 31.36 = 15.21 + 37.21 - 2 \cdot 3.9 \cdot 6.1 \cdot \cos(S) \]
   \[ 31.36 = 52.42 - 47.58 \cdot \cos(S) \]

5. Isolate \( \cos(S) \):
   \[ 31.36 - 52.42 = - 47.58 \cdot \cos(S) \]
   \[ -21.06 = - 47.58 \cdot \cos(S) \]
   \[ \cos(S) = \frac{21.06}{47.58} \]
   \[ \cos(S) \approx 0.4427 \
Transcribed Image Text:**Trigonometry Problem: Using the Law of Cosines to Find an Angle** In the given triangle \( \Delta RST \), the side lengths are as follows: \( r = 3.9 \) inches, \( s = 5.6 \) inches, and \( t = 6.1 \) inches. To find the measure of angle \( \angle S \) to the nearest 10th degree, you can use the Law of Cosines formula: \[ c^2 = a^2 + b^2 - 2ab \cdot \cos(C) \] Where \( a \), \( b \), and \( c \) are the sides of the triangle, and \( C \) is the angle opposite side \( c \). **Step-by-Step Solution:** 1. Identify the sides opposite to the angles: - In this case, let side \( r \) be opposite angle \( \angle R \), - side \( s \) be opposite angle \( \angle S \), - and side \( t \) be opposite angle \( \angle T \). 2. Rewrite the Law of Cosines for finding \( \angle S \): \[ s^2 = r^2 + t^2 - 2rt \cdot \cos(S) \] 3. Substitute the known values: \[ 5.6^2 = 3.9^2 + 6.1^2 - 2 \cdot 3.9 \cdot 6.1 \cdot \cos(S) \] 4. Calculate each term: \[ 31.36 = 15.21 + 37.21 - 2 \cdot 3.9 \cdot 6.1 \cdot \cos(S) \] \[ 31.36 = 52.42 - 47.58 \cdot \cos(S) \] 5. Isolate \( \cos(S) \): \[ 31.36 - 52.42 = - 47.58 \cdot \cos(S) \] \[ -21.06 = - 47.58 \cdot \cos(S) \] \[ \cos(S) = \frac{21.06}{47.58} \] \[ \cos(S) \approx 0.4427 \
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