若tana=3,则tan2a=
问题描述:
若tana=3,则tan2a=
答
tan2a
=2tana/(1-tan²a)
=2×3/(1-9)
=-3/4
若tana=3,则tan2a=
tan2a
=2tana/(1-tan²a)
=2×3/(1-9)
=-3/4