Posted by Anonymous on .
Use the Pythagorean identity to show that the double angle formula for cosine can be written as
a) cos2x = 1  2sin^2x
b) cos2x = 2cos^2x  1

advanced functions 
bobpursley,
sin^2x+ cos^2x=1
cos^2x+ sin^2x2sin^2x=12sin^2x
cos^2xsin^2x=12sin^2x
cos(2x)=12sin^2x