Obviously, a calculator cannot be used.
1) cos^-1(tan(37.5))
2) cos80deg(cos20deg) + sin80deg(sin20deg)
3) cos(tan^-1(-sqroot3))
4) The domain and range of tan(cos^-1(x/2)(2))
5) A formula for cos(30) in terms of cosX alone.
6) The period of 3cos (5(pi)x + 7)
Thanks and rep to anyone that solves any of these.