sin(2a+π/4）
=sin2acosπ/4+cos2asinπ/4
=√2/2(sin2a+cos2a)
=√2/2[2tana/(1+tan²a)+(1-tan²a)/(1+tan²a)]
=√2/2[(2tana+1-tan²a)/(1+tan²a) ]