已知tana=2,则sin^2a +sinacosa/sin^2+1的值
问题描述:
已知tana=2,则sin^2a +sinacosa/sin^2+1的值
答
sin^2a +sinacosa/sin^2+1?是sin^2a +sinacosa/sin^2a+1吧?sin^2a +sinacosa/sin^2a+1=sin^2a +sinacosa/(2sin^2a+cos^2a) (因为1=sin^2a+cos^2a)=tan^2a+tana/2tan^2a+1 (分子,分母同除以cos^2a)=6/9=2/3...