Okay these are giving me such a problem to figure out. I have to use these 4 identities to prove others.
A. sin(-x) = - sinx
B. cos(-x) = -cosx
C. cos(x+y) = cosxcosy-sinxsiny
D. sin(x+y) = sinxcosy + cosxsiny
these are what i have to derive.
Abslout value of cos(x/2) = Squareroot of ((1+cosx)/2)
Abslout value of sin(x/2) = Squareroot of ((1-cosx)/2)
Any help is much apprecieted. Thanks alot!