tana=根号2,sin2a=?
问题描述：
tana=根号2,sin2a=?
答
sin2a=2sinacosa
=2sinacosa/1
=2sinacosa/(sin²a+cos²a)=2 tana/( tan²a+1)
=2/3√2.
答
sin2a=2sinacosa
=2sinacosa/1
=2sinacosa/(sin²a+cos²a)
分子分母同除以cos²a得
=2 tana/( tan²a+1)
=2√2/3.