I'm very confused help....

I really don't understand how to prove trig identities can someone please explain thoroughly. Please help me with one or all below! ( Whoever explains all gets brainliest)


a) cosx / sin x = 1 / tan x

b) sin^2x / tan^2x = 1 - sin^2x

c) cosx = sin^3x / tanx + cos^3 x


Thanks!