今天作业最后一道数学题,困死了,懒得做,麻烦大大们了
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今天作业最后一道数学题,困死了,懒得做,麻烦大大们了
![](http://img.wesiedu.com/upload/5/d6/5d66d67b61ca14aee2a12325aa764412.jpg)
![](http://img.wesiedu.com/upload/5/d6/5d66d67b61ca14aee2a12325aa764412.jpg)
![今天作业最后一道数学题,困死了,懒得做,麻烦大大们了](/uploads/image/z/17726912-8-2.jpg?t=%E4%BB%8A%E5%A4%A9%E4%BD%9C%E4%B8%9A%E6%9C%80%E5%90%8E%E4%B8%80%E9%81%93%E6%95%B0%E5%AD%A6%E9%A2%98%2C%E5%9B%B0%E6%AD%BB%E4%BA%86%2C%E6%87%92%E5%BE%97%E5%81%9A%2C%E9%BA%BB%E7%83%A6%E5%A4%A7%E5%A4%A7%E4%BB%AC%E4%BA%86)
cos[sin(3π/2+θ)-1]?应该是cosθ[sin(3π/2+θ)-1]吧?!
sin(3π/2+θ)=-cosθ ,sin(π/2+θ)=cosθ
cos(π-θ)=-cosθ ,cos(π+θ)=-cosθ ,cos(2π-θ)=cosθ
左边=[(-cosθ)/cosθ(-cosθ-1)] + [cosθ/(-cosθ)·cosθ-(-cosθ)]
=1/(cosθ+1) + 1/(1-cosθ)
=(1-cosθ)/(1+cosθ)(1-cosθ) + (1+cosθ)/(1-cosθ)(1+cosθ)
=(1-cosθ+1+cosθ)/(1-cos²θ)
=2/sin²θ=右边
sin(3π/2+θ)=-cosθ ,sin(π/2+θ)=cosθ
cos(π-θ)=-cosθ ,cos(π+θ)=-cosθ ,cos(2π-θ)=cosθ
左边=[(-cosθ)/cosθ(-cosθ-1)] + [cosθ/(-cosθ)·cosθ-(-cosθ)]
=1/(cosθ+1) + 1/(1-cosθ)
=(1-cosθ)/(1+cosθ)(1-cosθ) + (1+cosθ)/(1-cosθ)(1+cosθ)
=(1-cosθ+1+cosθ)/(1-cos²θ)
=2/sin²θ=右边