(sin(x)+cos(x))^2=sin^2x+2sin(x)cos(x)+cos^2x=1+2sin(x)cos(x)=(2/5)^2=4/25
2 sin(x)cos(x)=4/25-1=-21/25
sin(x)cos(x)=-21/50=-0,42
(sin(x)+cos(x))^2=sin^2x+2sin(x)cos(x)+cos^2x=1+2sin(x)cos(x)=(2/5)^2=4/25
2 sin(x)cos(x)=4/25-1=-21/25
sin(x)cos(x)=-21/50=-0,42