tana=根号2,sin2a=?

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tana=根号2,sin2a=?tana=根号2,sin2a=?tana=根号2,sin2a=?sin2a=2sinacosa=2sinacosa/1=2sinacosa/(sin²a+co

tana=根号2,sin2a=?
tana=根号2,sin2a=?

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

sin2a=2sinacosa
=2sinacosa/1
=2sinacosa/(sin²a+cos²a)=2 tana/( tan²a+1)
=2/3√2.