1. Today in Precalculus Go over homework
Proving trig identities (no handout)
Homework
Quiz Friday

2. Guidelines for Verifying Trig Identities
Work with one side at a time, start with the more complicated side & note what functions you are trying to get to.
If you have negative angles, use odd/even identities first.
Try to factor, add fractions, FOIL or find the LCD.
When in doubt, try converting everything in terms of sin & cos.
DO NOT CROSS MULTIPLY OR ADD/SUBTRACT FROM BOTH SIDES: you CANNOT assume they are equal until you prove they are equal.

7. Practice
secxcosx = 1
cos2x – sin2x = 2cos2x - 1

8. Quiz Friday, March 3