Trig Identities....Half Angles help PLEASEEEEE!!!
Can someone explain what the teacher wrote on the board for me please???
Cos2A = cos^2A-sin^2A
= 1 - 2sin^2 A (What happened here???????)
now do same thing with 1-sin^2= cos^2
and you should get the identity you teacher wrote
sooooo
1-sin^2=cos^2
sub into
Cos2A = cos^2A-sin^2A
Cos2A=1-sin^2A-sin^A
==1-2sin^2A