tga=1/2,sin2a sin^2a=?

问题描述:

tga=1/2,sin2a sin^2a=?

sin2a=2sina*cosa=2sina*cosa/1=2sina*cosa/(sin^2a+cos^2a) =2tana/(tan^2a+1)=4/5 sin2asin^2a=4/5×16/25=64/125