已知tan@=3,求2/3sin^2@+1/4cos^2@的值.
问题描述：
已知tan@=3,求2/3sin^2@+1/4cos^2@的值.
答
tan@=3
(cos@)^2=1/(1+(tan@)^2)=1/10
(sin@)^2=9/10
(2/3)(sin@)^2+(1/4)(cos@)^2
=3/20+1/40
=7/40