(sin x + cos x)² = 1+ sin x cos x
sin x² +2sin x cos x+cos x²=1+sin x cos x
1+sin 2x =1+sin x cos x
sin 2x=sin x cos x
sin 2x-sin x cos x=0
2 sin x cos x - sin x cos x=0
sin x cos x=0
sin x=0 cos x=0
x=kπ, k∈Z x=π/2 +kπ, k∈Z
x=kπ/2, k∈Z
sin^2x+cos^2x+2sinxcosx=1+sinxcosx
1+2sinxcosx=1+sinxcosx
sinxcosx=0
sinx=0
x=пn , n∈Z
cosx=0
x=п/2 +пn, n∈Z
x=пn/2
