1 + sin7x = (cos3x/2 + sin3x/2) ^2

1+sin7x=sin^{2} / frac{3x}{2} - 2sin/frac{3x}{2}cos/frac{3x}{2}+cos^{2} / frac{3x}{2} / / sin7x+sin3x=0 / / 2sin (5x) cos (2x) = 0 / / 5x = / pi n / / x = / frac{/pi n}{5} / / 2x = / frac{ / pi }{2} + / pi k/ / x = / frac{ / pi }{4} + / frac{ / pi k}{2}

k ∈ Z

n ∈ Z