( tan A+cot A)cosA sin A- cos

(tan A + cot A) cos A sin A - cos^2 A = (sin A/ cos A + cos A/sin A) cos A sin A - cos^2 A = (sin^2 A + cos^2 A / sin A cos A) cos A sin A - cos^2 A = sin^2 A + cos^2 A - cos^2 A = sin^2 A
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