Explanation

Trig identities are used to:

• Simplify expressions

• Verify equations

• Solve trig equations

Important rule:
You never change the value, only the form.

Example:
1 − sin²(θ)
→ cos²(θ)

Quiz

1. What is a trigonometric identity?

2. Can identities change the value of an expression?

3. Name a common trig identity.

4. Why are identities useful?

5. Do identities apply for all θ?

Answer Key

1. An equation true for all valid θ

2. No

3. sin²(θ) + cos²(θ) = 1

4. Simplification and solving

5. Yes