Addition formulas

These are forumulas used to simplify and evaluate trignomic equations. You are given instructions with a trig function and you plug into formulas. Sometimes you may need to find a reference angle before plugging in. Formulas can be used both backwards and like they are.
They can also be negative if necessary.

1.cos(@+B)=cos@ cosB + sin@ sinB

2.sin(@+B)=sin@ cosB + cos@ sinB

3.sinX+sinY = 2sin X+Y/2 cos X-Y/2

4.sinX-sinY = 2cos X+Y/2 sin X-Y/2

5.cosX+cosY = 2cos X+Y/2 sin X-Y/2

6.cosX-cosY = -2sin X+Y/2 sin X-Y/2

Ex1. sin (75)
a.Must first get two angels for formula: sin(45+30)
b.Then plug into formula: sin45 cos30 + cos45 sin30
c.Use trig chart to get value. (square root2/2) (square root 3/2) +
(square root2/2) (1/2)
=square root4/4