Verified answer

cos(2x) = cos²(x) - sen²(x)

cos²(x) - sen²(x) + sen²(x) + cos(x) = 0

cos²(x) + cos(x) = 0

cos(x)*(cos(x) + 1) = 0

cos(x) = 0 ---> x = pi/2 ou x = 3pi/2

cos(x) + 1 = 0

cos(x) = -1 --> x = pi

pronto

Cos2x+sen²x+cosx=

Cos²x-Sen²x+sen²x+cosx

cos²x+cosx

cosx(cosx+1)=0

cosx=0 --> 90 graus

cosx+1=-1 --> 180 graus