1.(1-sint)(1+sint)=? 2.(cosx+1/2)(cosx-1)=0

1)  (1 - sint)*(1 + sint) = 0 a) 1 - sint = 0  sint = 1 t = π/4 + πk, k∈Z b) 1 + sint = 0  sint = - 1 t = - π/4 + πn, n∈Z   2)  (cosx + 1/2)(cosx - 1 )= 0 a) cosx + 1/2 = 0  cosx = - 1/2 x = (+ -)arccos(-1/2) + 2πn, n∉Z x = (+ -)*(π - arccos(1/2)) + 2πn, n∉Z x = (+ -)*(π - π/3) + 2πn, n∉Z x = (+ -)*(2π/3) + 2πn, n∉Z b)  cosx - 1 = 0 cosx = 1 x = 2πk, k∈Z