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