已知tana=-4/3,则sin2a=.

问题描述:

已知tana=-4/3,则sin2a=.

sin2a
=2sinacosa
=2sinacosa/(sin²a+cos²a)
分子分母同时除以cos²a
=2tana/(tan²a+1)
=2*(-4/3)/[(16/9+1]
=-24/(16+9)
=-24/25