ㅠ If sin x 2 the number A = A cos x, then

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°.
Question
If \(\sin \left( x - \frac{\pi}{2} \right) = A \cos x\), then the number \(A =\) [ ].

---

**Explanation:**

This mathematical expression is asking to find the value of \(A\) that satisfies the equation \(\sin \left( x - \frac{\pi}{2} \right) = A \cos x\). 

### Steps to Solve:

1. **Use Trigonometric Identity:**
   - The identity for the sine of a difference is:
     \[
     \sin(a - b) = \sin a \cos b - \cos a \sin b
     \]
   - Apply this identity to \(\sin(x - \frac{\pi}{2})\):
     \[
     \sin(x) \cos\left(\frac{\pi}{2}\right) - \cos(x) \sin\left(\frac{\pi}{2}\right)
     \]

2. **Substitute Known Values:**
   - \(\cos\left(\frac{\pi}{2}\right) = 0\)
   - \(\sin\left(\frac{\pi}{2}\right) = 1\)
   - Therefore:
     \[
     \sin(x) \cdot 0 - \cos(x) \cdot 1 = -\cos(x)
     \]

3. **Equate and Solve:**
   - The equation becomes:
     \[
     -\cos(x) = A \cos(x)
     \]
   - Divide both sides by \(\cos(x)\) (assuming \(\cos(x) \neq 0\)):
     \[
     A = -1
     \]

Thus, the number \(A\) is \(-1\).
Transcribed Image Text:If \(\sin \left( x - \frac{\pi}{2} \right) = A \cos x\), then the number \(A =\) [ ]. --- **Explanation:** This mathematical expression is asking to find the value of \(A\) that satisfies the equation \(\sin \left( x - \frac{\pi}{2} \right) = A \cos x\). ### Steps to Solve: 1. **Use Trigonometric Identity:** - The identity for the sine of a difference is: \[ \sin(a - b) = \sin a \cos b - \cos a \sin b \] - Apply this identity to \(\sin(x - \frac{\pi}{2})\): \[ \sin(x) \cos\left(\frac{\pi}{2}\right) - \cos(x) \sin\left(\frac{\pi}{2}\right) \] 2. **Substitute Known Values:** - \(\cos\left(\frac{\pi}{2}\right) = 0\) - \(\sin\left(\frac{\pi}{2}\right) = 1\) - Therefore: \[ \sin(x) \cdot 0 - \cos(x) \cdot 1 = -\cos(x) \] 3. **Equate and Solve:** - The equation becomes: \[ -\cos(x) = A \cos(x) \] - Divide both sides by \(\cos(x)\) (assuming \(\cos(x) \neq 0\)): \[ A = -1 \] Thus, the number \(A\) is \(-1\).
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