Prove that the following identity is true.   sin4 t - cos4 t / sin2 t cos2 t = sec2 t - csc2 t

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

Prove that the following identity is true.

 

sin4 t - cost / sin2 t cos2 t = sec2 t - csc2 t

The equation shown is:

\[
\frac{\sin^4 t - \cos^4 t}{\sin^2 t \cos^2 t} = \sec^2 t - \csc^2 t
\]

### Explanation:

This mathematical expression involves trigonometric identities:

1. **Numerator:** \(\sin^4 t - \cos^4 t\) is a difference of squares, which can be factored as \((\sin^2 t + \cos^2 t)(\sin^2 t - \cos^2 t)\). Using the Pythagorean identity, \(\sin^2 t + \cos^2 t = 1\), the numerator simplifies to \(\sin^2 t - \cos^2 t\).

2. **Denominator:** \(\sin^2 t \cos^2 t\) is a product of squares of the sine and cosine functions.

3. **Right Side of the Equation:** The expression \(\sec^2 t - \csc^2 t\) involves the secant and cosecant functions, which are reciprocals of cosine and sine, respectively. The identity can further be explored using \(\sec^2 t = 1/\cos^2 t\) and \(\csc^2 t = 1/\sin^2 t\).

### Educational Purpose: 

This equation showcases the application of trigonometric identities and algebraic manipulation in simplifying and equating trigonometric expressions. It's a great example for exploring the connections between different trigonometric functions and identities.
Transcribed Image Text:The equation shown is: \[ \frac{\sin^4 t - \cos^4 t}{\sin^2 t \cos^2 t} = \sec^2 t - \csc^2 t \] ### Explanation: This mathematical expression involves trigonometric identities: 1. **Numerator:** \(\sin^4 t - \cos^4 t\) is a difference of squares, which can be factored as \((\sin^2 t + \cos^2 t)(\sin^2 t - \cos^2 t)\). Using the Pythagorean identity, \(\sin^2 t + \cos^2 t = 1\), the numerator simplifies to \(\sin^2 t - \cos^2 t\). 2. **Denominator:** \(\sin^2 t \cos^2 t\) is a product of squares of the sine and cosine functions. 3. **Right Side of the Equation:** The expression \(\sec^2 t - \csc^2 t\) involves the secant and cosecant functions, which are reciprocals of cosine and sine, respectively. The identity can further be explored using \(\sec^2 t = 1/\cos^2 t\) and \(\csc^2 t = 1/\sin^2 t\). ### Educational Purpose: This equation showcases the application of trigonometric identities and algebraic manipulation in simplifying and equating trigonometric expressions. It's a great example for exploring the connections between different trigonometric functions and identities.
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