ind the exact value of tan 2 cos y² = 25 y = 5 12 [2 COB-¹ (-17/13)] - y Since x=-12 and y = 5, tan 0 = X tan (20). tan (20) = 2 tan 0 1- tan ²0 2 (-=-512 1-(-=-172) 120 119 5 -12 100 Substitute tan 8 = 5

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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How do you get negative 120 over 119?
**Example Problem: Finding the Exact Value of a Trigonometric Expression**

**Problem:**
Find the exact value of \( \tan \left[ 2 \cos^{-1} \left( -\frac{12}{13} \right) \right] \).

**Solution:**

1. **Determine \( y \):**
   \[
   y^2 = 25 \quad \Rightarrow \quad y = 5
   \]

2. **Find \( \tan \theta \):**
   Given \( x = -12 \) and \( y = 5 \):
   \[
   \tan \theta = \frac{y}{x} = \frac{5}{-12} = -\frac{5}{12}
   \]
   Substitute \( \tan \theta = -\frac{5}{12} \) into the formula for \( \tan (2\theta) \).

3. **Use the Double Angle Formula for Tangent:**
   \[
   \tan (2\theta) = \frac{2 \tan \theta}{1 - \tan^2 \theta}
   \]
   Substitute \( \tan \theta = -\frac{5}{12} \):
   \[
   \tan (2\theta) = \frac{2 \left( -\frac{5}{12} \right)}{1 - \left(-\frac{5}{12}\right)^2}
   \]
   \[
   = \frac{-\frac{10}{12}}{1 - \frac{25}{144}}
   \]
   \[
   = \frac{-\frac{10}{12}}{\frac{119}{144}}
   \]
   Simplify to:
   \[
   = -\frac{120}{119}
   \]

4. **Conclusion:**
   \[
   \tan \left[ 2 \cos^{-1} \left( -\frac{12}{13} \right) \right] = -\frac{120}{119}
   \]

This solution applies trigonometric identities and properties to solve for the exact value of the given expression.
Transcribed Image Text:**Example Problem: Finding the Exact Value of a Trigonometric Expression** **Problem:** Find the exact value of \( \tan \left[ 2 \cos^{-1} \left( -\frac{12}{13} \right) \right] \). **Solution:** 1. **Determine \( y \):** \[ y^2 = 25 \quad \Rightarrow \quad y = 5 \] 2. **Find \( \tan \theta \):** Given \( x = -12 \) and \( y = 5 \): \[ \tan \theta = \frac{y}{x} = \frac{5}{-12} = -\frac{5}{12} \] Substitute \( \tan \theta = -\frac{5}{12} \) into the formula for \( \tan (2\theta) \). 3. **Use the Double Angle Formula for Tangent:** \[ \tan (2\theta) = \frac{2 \tan \theta}{1 - \tan^2 \theta} \] Substitute \( \tan \theta = -\frac{5}{12} \): \[ \tan (2\theta) = \frac{2 \left( -\frac{5}{12} \right)}{1 - \left(-\frac{5}{12}\right)^2} \] \[ = \frac{-\frac{10}{12}}{1 - \frac{25}{144}} \] \[ = \frac{-\frac{10}{12}}{\frac{119}{144}} \] Simplify to: \[ = -\frac{120}{119} \] 4. **Conclusion:** \[ \tan \left[ 2 \cos^{-1} \left( -\frac{12}{13} \right) \right] = -\frac{120}{119} \] This solution applies trigonometric identities and properties to solve for the exact value of the given expression.
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