Answer
$sin~φ(csc~φ-sin~φ)=cos^2φ$
Work Step by Step
We know that:
$csc~φ=\frac{1}{sin~φ}$
$sin^2φ+cos^2φ=1$
$cos^2φ=1-sin^2φ$
So:
$sin~φ(csc~φ-sin~φ)=sin~φ(\frac{1}{sin~φ}-sin~φ)=1-sin^2φ=cos^2φ$
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