已知sina+cosa/sina-cosa=2,计算下列各式的值（1）3sina+cosa/2sina+3cosa(2)sin^a-2sinacosa+1.

题目

已知sina+cosa/sina-cosa=2,计算下列各式的值（1）3sina+cosa/2sina+3cosa(2)sin^a-2sinacosa+1.

答案

sina+cosa/sina-cosa=2分子分母同时除以cosa(tana+1)/(tana-1)=2∴ tana=3(1)3sina+cosa/2sina+3cosa分子分母同时除以cosa=(3tana+1)/(2tana+3)=(3*3+1)/(2*3+3)=10/9(2)sin^a-2sinacosa+1=(sin^a-2sinacosa)/(sin&#...