evaluate and simplify the function of f(x) = cos 2x (a) f((π) (b) f(-π/4)
cos(2π) = 1
cos(-π/2) = 0
not sure how to simplify those values ...
I guess maybe you wanted to apply the double-angle formula
cos(2x) = cos^2x - sin^2x = 2cos^2x - 1 = 1 - 2sin^2x
but I see no point in doing all that algebra.