>>583
∫[x=0〜π/4] sin(2x)*cos(x)dx=(1/2)∫[x=0〜π/4] sin(3x)+sin(x) dx
=-(1/2){cos(3x)/3+cos(x)}_[x=0〜π/4]=-(1/2){cos(3x)/3+cos(x)}_[x=0〜π/4]=(4-√2)/3