tan(π/4+a)=2
所以cos2a=sin(π/2+2a)=(2×2)/(1+2²)=4/5
sin2a=-cos(π/2+2a)=-(1-2²)/(1+2²)=3/5
原式=sin2a+2/(1+cos2a)=3/5+10/9=77/45