(cosx-sinx)(cosx+sinx)=cos3п/4

Решение(cosx - sinx)(cosx + sinx) = cos(3π/4)cos²x - sin²x = - √2/2cos2x = - √2/22x = (+ -)arccos(-√2/2) + 2πk, k∈Z2x = (+ -)(π - π/4) + 2πk, k∈Z2x = (+ -)3π/4 + 2πk, k∈Zx = (+ -)3π/8 + πk, k∈Z