Решение смотри на фотографии
<span>у = 1,4 х - 2,6 и у = 3,4 - 1,6 х
1.4x -2.6 = 3.4 -1.6x
1.4x +1.6x = 3.4 +2.6
3x = 6
x = 6/3
x = 2
Ответ С</span>
Sin²x+sin²y+2cos(x+y+x-y)/2*cos(x+y-x+y)/2=
=sin²x+sin²y+1/2(cosx(x+y-x+y)+cos(x+y+x-y))=
=sin²x+sin²y+1/2(cos2x+cos2y)=sin²x+sin²y+1/2-sin²x+1/2-sin²y=1