tan(90-2arctan1/2)
问题描述:
tan(90-2arctan1/2)
答
令a=arctan1/2
tana=1/2
所以tan(2a)=2tana/(1-tan²a)=4/3
原式=tan(90-2a)
=cot2a
=1/tan2a
=3/4