Question

cos 105 скажите пожаааалуйста

Answer 1

cos 105=cos(90+15)=cos90cos15-sin90sin15=-sin15=-sin(45-30)=-(sin45cos30-cos45sin30)=
=-(sqrt(2)/2*sqrt(3)/2-sqrt(2)/2*1/2)=-(sqrt(6)/4-sqrt(2)/4)=-0.2588

Answer 2

cos105°=cos(60°+45°)=cos60°*cos45° - sin60°*sin45°=
= (1/2)*(√2/2) - (√3/2)*(√2/2) = √2(1-√3)/4