1. Proving trigonometric identities, part II
Section 5.2b

2. Let’s start with this… Prove the identity: Setting up a difference
of squares
Pythagorean
Identity
 Answer

3. General Strategies III
1. Use the algebraic identity
to set up applications of the Pythagorean identities.
2. Always be mindful of the “target” expression, and
favor manipulations that bring you closer to your goal.
Sometimes it’s even helpful to work from both
sides towards a common intermediate expression…

4. Working from Both Sides
Prove the identity:
Start on the LHS:
Not clear how to get
from here to the RHS…
Instead, let’s bring the RHS to this expression!!!

5. Working from Both Sides
Prove the identity:
Simplifying the RHS:
We can now combine both parts for a complete proof.

7. A Plethora of Practice Problems
Prove the identity:

8. A Plethora of Practice Problems
Prove the identity:

9. A Plethora of Practice Problems
Prove the identity:

10. A Plethora of Practice Problems
Prove the identity: