(sin x+ cos x)^2=1+cos x

sin^2x+2sinxcosx+cos^2=1-cosx
1+2sinxcosx=1-cos
2sinxcosx=-cosx
2sinxcosx+cosx=0
cosx (2sinx+1)=0
cosx=0
x1=п/2+пn
2sinx+1=0
sinx=-1/2
x2=-п/6+2пn