7.3

7.3  The Addition and Subtraction Formulas

Addition and subtraction formulas can help you to find exact values of trigonometric equations, solve for identities, etc.

http://math.ucsd.edu/~wgarner/math4c/textbook/chapter6/addsubformulas.htm <= good site to see how these formulas are derived

Cosine Formulas
cos(x + y) = cosx cosy - sinx siny
 cos(x - y) = cosx cosy + sinx siny


Sine Formulas
sin(x + y) = siny cosx + cosy sinx
sin(x - y) = siny cosx - cosy sinx


Tangent Formlas






Examples of how to apply the formulas:

 Cofunction Formulas:  In these formulas, 'u' is a variable that is taking place for a real number or radian measure of an angle

 -Hannah