sin* (t) – cos*(t) – cos²(t) = 1 sin²(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°.
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**Objective:**

Show that 

\[
\frac{\sin^4(t) - \cos^4(t)}{\sin^2(t) - \cos^2(t)} = 1
\]

**Explanation:**

We start by recognizing the expression \(\sin^4(t) - \cos^4(t)\) as a difference of squares:

\[
\sin^4(t) - \cos^4(t) = (\sin^2(t))^2 - (\cos^2(t))^2 = (\sin^2(t) - \cos^2(t))(\sin^2(t) + \cos^2(t))
\]

Since \(\sin^2(t) + \cos^2(t) = 1\) (using the Pythagorean identity), the expression simplifies to:

\[
\sin^4(t) - \cos^4(t) = (\sin^2(t) - \cos^2(t)) \cdot 1
\]

Thus, we can rewrite the original expression as:

\[
\frac{(\sin^2(t) - \cos^2(t)) \cdot 1}{\sin^2(t) - \cos^2(t)}
\]

This simplifies to 1, given that \(\sin^2(t) - \cos^2(t) \neq 0\):

\[
\frac{\sin^2(t) - \cos^2(t)}{\sin^2(t) - \cos^2(t)} = 1
\]

Therefore, the equality is proven.

---

In this mathematical proof, recognizing and applying the identity for the difference of squares and the Pythagorean identity are key steps in simplifying the expression.
Transcribed Image Text:**Objective:** Show that \[ \frac{\sin^4(t) - \cos^4(t)}{\sin^2(t) - \cos^2(t)} = 1 \] **Explanation:** We start by recognizing the expression \(\sin^4(t) - \cos^4(t)\) as a difference of squares: \[ \sin^4(t) - \cos^4(t) = (\sin^2(t))^2 - (\cos^2(t))^2 = (\sin^2(t) - \cos^2(t))(\sin^2(t) + \cos^2(t)) \] Since \(\sin^2(t) + \cos^2(t) = 1\) (using the Pythagorean identity), the expression simplifies to: \[ \sin^4(t) - \cos^4(t) = (\sin^2(t) - \cos^2(t)) \cdot 1 \] Thus, we can rewrite the original expression as: \[ \frac{(\sin^2(t) - \cos^2(t)) \cdot 1}{\sin^2(t) - \cos^2(t)} \] This simplifies to 1, given that \(\sin^2(t) - \cos^2(t) \neq 0\): \[ \frac{\sin^2(t) - \cos^2(t)}{\sin^2(t) - \cos^2(t)} = 1 \] Therefore, the equality is proven. --- In this mathematical proof, recognizing and applying the identity for the difference of squares and the Pythagorean identity are key steps in simplifying the expression.
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