tana=3,则sin平方a-cos平方a=详细过程谢谢..
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![tana=3,则sin平方a-cos平方a=详细过程谢谢..](/uploads/image/z/1055411-35-1.jpg?t=tana%3D3%2C%E5%88%99sin%E5%B9%B3%E6%96%B9a-cos%E5%B9%B3%E6%96%B9a%3D%E8%AF%A6%E7%BB%86%E8%BF%87%E7%A8%8B%E8%B0%A2%E8%B0%A2..)
tana=3,则sin平方a-cos平方a=详细过程谢谢..
tana=3,则sin平方a-cos平方a=详细过程谢谢..
tana=3,则sin平方a-cos平方a=详细过程谢谢..
sin平方a-cos平方a
=(sin平方a-cos平方a)/(sin平方a+cos平方a)
=(tan平方a-1)/(tan平方a+1)
=(9-1)/(9+1)
=4/5
(sinα)^2 - (cosα)^2
=(cosα * tanα)^2 - (cosα)^2
=(cosα)^2 * [(tanα)^2 - 1]
= 1/(secα)^2 * [(tanα)^2 -1]
= [(tanα)^2 -1]/[(tanα)^2 + 1] 注:secα = 1/cosα,(secα)^2 = 1+(tanα)^2
= [3^2 -1]/[3^2 + 1]
=8/10 = 4/5