Prove that (+costheta)/(1-costheta) -(1-costheta)/(1+costheta) = 4cotthetacosectheta

Prove that (+costheta)/(1-costheta) -(1-costheta)/(1+costheta) = 4cott

1.	Prove that (+costheta)/(1-costheta) -(1-costheta)/(1+costheta) = 4cotthetacosectheta
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