i have 3 questions i am stuck on for homework and i have a test on this monday. if someone would be able to solve them I would appreciate it

cotx(tany+tanx/coty+cotx) = tany

cosx+cos2x+cos3x = cos2x(1+2cosx)

sin^3x+sin^3x/sinx+cosx = 1-sinxcosx

Thanks