Double-Angle And Half-Angle Formulas

This week we learned about Double- Angle and Half-Angle formulas. 

Double-Angle Formulas:

sin2(alpha)=2sin(alpha)cos(alpha)

cos2(alpha)=cos^2(alpha)-sin^2(alpha)

cos2(alpha)=1-sin^2(alpha)

cos2(alpha)=2cos^2(alpha)-1

tan2(alpha)=2tan(alpha)/1-tan^2(alpha)

Half-Angle Formulas:

sin(alpha)/2=+/-square root of 1-cos(alpha)/2

cos(alpha)/2=+/- square root of 1+cos(alpha)/2

tan(alpha)/2=+/- square root of 1-cos(alpha)/1+cos(alpha)

tan(alpha)/2=sin(alpha)/ 1+cos(alpha)

tan(alpha)/2=1-cos(alpha)/ sin(alpha)

Steps: 

1- Figure out which formulas going to be used

2- Fill in the formula

3- Simplify

4- Work