1-sin2a=ctg2a*sin2a упростить

sin^2 (a) - 2sinacosa+cos^ (a) = cos2a/sin2a*sin2a

cos^2 (a) + sin^2 (a) - sin2a=cos2a

cos^2 (a) + sin^ (a) - sin2a-cos^2 (a) + sin^2 (a) = 0

2sin^2 (a) - sin2a=0

2sin^2 (a) - 2sinacosa=0

2sina (sina-cosa) = 0

1) 2sina=0 2) sina-cosa=0 делит на sina

sina=0 tga-1=0

a=пn tga=1

х=п/4+пn