Question

cos (70градусов + x) * cos (20градусов -x)=0,5

Answer 1

ответ будет таким

=0.41027

Answer 2

$cos(70^o+x)*cos(20^o-x)=0.5;\ cos(70^o+x)*cos(90^o-(70^0+x))=0.5;\ cos(70^o+x)*sin(70^0+x)=0.5;\ 2*cos(70^o+x)*sin(70^0+x)=2*0.5;\ sin(2*(70^o+x))=1;\ sin(140^0+2x)=1;\ 140^o+2x=90^o+360^o*k;\ 2x=-140^0+90^o+360^o*k;\ 2x=-50^0+360^o*k;\ x=-25^0+180^o*k;$

k є Z