MAT129 Fall 2025 Notes mathnstuff.com/math/precalc/MAT129fa25/p.21.htm © 2025   A2, Agnes Azzolino Sum and Difference and Multiple-Angle Formulas, Text 9.2,9.3,9.4, PG. 706, 720, 732

Welcome to Precalc! More Identities Hi,     Today's identities are found on the "cheat sheets" I suggest my calc I students have handy.             Contact me through the pink box on www.mathnstuff.com/math/math.htm or with the phone number on your CANVAS course home page.     Stay safe, A2

9.2  - Sum and Difference Identities, pg. 706,  Learning Objectives
	* Use sum and difference formulas for cosine.
	* Use sum and difference formulas for sine.
	* Use sum and difference formulas for tangent.
	* Use sum and difference formulas for cofunctions.
	* Use sum and difference formulas to verify identities.
9.3  - Double-Angle, Half-Angle, and Reduction Formulas, pg. 720,  Learning Objectives
	* Use double-angle formulas to find exact values.
	* Use double-angle formulas to verify identities.
	* Use reduction formulas to simplify an expression.
	* Use half-angle formulas to find exact values.
9.4  - Sum-to-Product and Product-to-Sum Formulas, pg 732,  Learning Objectives
	* Express products as sums.
	* Express sums as products.

Proof of sin(A + B), cos(A+B) -- the sine of the sum and cosine of the sum of two angles

"cheat sheets"