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