Prove the identity. sin (x+y) = tanx+ tan y cosx cosy Note that each Statement must be based on a Rule chosen from the Rule menu. To see a detailer select the More Information Button to the right of the Rule. Statement Rule sin (x + y) cos x cos y %3D Select Rule

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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### Proving Trigonometric Identities

To prove the given identity:

\[
\frac{\sin (x + y)}{\cos x \cos y} = \tan x + \tan y
\]

Follow these steps:

1. **Understand the Formula:**
   - The left-hand side (LHS) of the identity is \(\frac{\sin (x + y)}{\cos x \cos y}\).
   - The right-hand side (RHS) of the identity is \(\tan x + \tan y\).

2. **Using the Angle Sum Identity:**
   - The sine of the sum of two angles can be expressed by the formula:
     \[
     \sin (x + y) = \sin x \cos y + \cos x \sin y
     \]

3. **Substitute in the Identity:**
   - Replace \(\sin (x + y)\) in the original identity with \(\sin x \cos y + \cos x \sin y\):
     \[
     \frac{\sin x \cos y + \cos x \sin y}{\cos x \cos y}
     \]

4. **Simplify the Expression:**
   - Split the fraction into two parts:
     \[
     = \frac{\sin x \cos y}{\cos x \cos y} + \frac{\cos x \sin y}{\cos x \cos y}
     \]
   - Simplify each part of the expression:
     \[
     = \frac{\sin x}{\cos x} + \frac{\sin y}{\cos y}
     \]
   - Use the definitions of the tangent function:
     \[
     = \tan x + \tan y
     \]

This confirms that:

\[
\frac{\sin (x + y)}{\cos x \cos y} = \tan x + \tan y
\]

### Note:
- Each Statement must be based on a Rule chosen from the Rule menu. For a detailed understanding of each rule, select the "More Information" Button to the right of the Rule.

#### Diagram Explanation:
- The lower portion of the image includes a user interface element where users can select the rule used to validate each step of the proof. The "Validate" button allows submission to check if the chosen rule is correct. There is a section titled "Statement" which currently contains the given identity waiting
Transcribed Image Text:### Proving Trigonometric Identities To prove the given identity: \[ \frac{\sin (x + y)}{\cos x \cos y} = \tan x + \tan y \] Follow these steps: 1. **Understand the Formula:** - The left-hand side (LHS) of the identity is \(\frac{\sin (x + y)}{\cos x \cos y}\). - The right-hand side (RHS) of the identity is \(\tan x + \tan y\). 2. **Using the Angle Sum Identity:** - The sine of the sum of two angles can be expressed by the formula: \[ \sin (x + y) = \sin x \cos y + \cos x \sin y \] 3. **Substitute in the Identity:** - Replace \(\sin (x + y)\) in the original identity with \(\sin x \cos y + \cos x \sin y\): \[ \frac{\sin x \cos y + \cos x \sin y}{\cos x \cos y} \] 4. **Simplify the Expression:** - Split the fraction into two parts: \[ = \frac{\sin x \cos y}{\cos x \cos y} + \frac{\cos x \sin y}{\cos x \cos y} \] - Simplify each part of the expression: \[ = \frac{\sin x}{\cos x} + \frac{\sin y}{\cos y} \] - Use the definitions of the tangent function: \[ = \tan x + \tan y \] This confirms that: \[ \frac{\sin (x + y)}{\cos x \cos y} = \tan x + \tan y \] ### Note: - Each Statement must be based on a Rule chosen from the Rule menu. For a detailed understanding of each rule, select the "More Information" Button to the right of the Rule. #### Diagram Explanation: - The lower portion of the image includes a user interface element where users can select the rule used to validate each step of the proof. The "Validate" button allows submission to check if the chosen rule is correct. There is a section titled "Statement" which currently contains the given identity waiting
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