解
(1)原式
=(tana+tanπ/4)/(1-tanatanπ/4)
=(-2+1)/(1+2)
=-1/3
(2)原式
=(2sinacosa+cos²a-sin²a)/(sin²a+cos²a)——除以sin²a+cos²a=1,值不變
=(2tana+1-tan²a)/(tan²a+1)——分子分母同時除以cos²a
=(-4+1-4)/(4+1)
=-7/5