5srtq2sin3П/8*cos3П/8
5√2*1/2*2*sin3П/8*cos3П/8=(5√2/2)*sin(2*3П/8)=(5√2/2)*sin(6П/8)= =(5√2/2)*sin(3П/4)=(5√2/2)*√2/2=5/2=2,5