tana=2,则cos^2a=多少1tana=2,则cos^2a=
问题描述:
tana=2,则cos^2a=多少1
tana=2,则cos^2a=
答
cos^2 a
=1/sec^2 a
=1/(1+tan^2 a)
=1/(1+4)
=1/5