Ответ:
Объяснение: sin2a=2sin(a)cos(a)
cos2a=cos²(a) -sin²(a)
sin²a+cos²a=1
sin2(x/2) -cos2*(x/2) =sin²(x/2)+cos²(x/2) ;
2sin(x/2) cos(x/2)-(cos²(x/2) -sin²(x/2)) =sin²(x/2) +cos²(x/2) ;
2sin(x/2) cos(x/2)-cos²(x/2) +sin²(x/2)) -sin²(x/2) -cos²(x/2)=0 ;
2sin(x/2) cos(x/2)-2cos²(x/2) =0 ; разделим 2сos²(x/2) ≠0
sin(x/2) /(cos(x/2)) -1=0;
tg(x/2) =1
(x/2) =arcctg(1) +πn, n€Z
x/2=(π/4) +πn, n€Z |домножим на 2
Х=(π/2) +2πn, n€Z