已知3sina=-cosa,求值 (1)sina-3cosa/sina+3cosa (2)1+sinacosa
问题描述:
已知3sina=-cosa,求值 (1)sina-3cosa/sina+3cosa (2)1+sinacosa
答
3sina=-cosasina/cosa=-1/3∴tana=-1/3 (1)sina-3cosa/sina+3cosa =(tana-3)/(tana+3)=(-1/3-3)/(-1/3+3)=-5/4 (2)1+sinacosa=(sin²a+cos²a+sinacosa)/(sin²a+cos²a)=(tan²a+1+tana)/(...