L=1+ctg^2\alpha=\sin^2\alpha+\cos^2\alpha+\frac{\cos^2\alpha}{\sin^2\alpha}=\frac{\sin^2\alpha(\cos^2\alpha+\sin^2\alpha)+\cos^2\alpha}{\sin^2\alpha}=\frac{\sin^2\alpha+\cos^2\alpha}{\sin^2\alpha}=\frac{1}{\sin^2\alpha}=P
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L=\sin^4\alpha-\cos^4\alpha=(\sin^2\alpha+\cos^2\alpha)(\sin^2\alpha-\cos^2\alpha)=1*(\sin^2\alpha-\cos^2\alpha)=\sin^2\alpha-\cos^2\alphaP