1) (sec - cos) / tan = sin 2) (csc^2 - 1) / csc^2 = cos^2 3) (sin/csc) - 1 = -cos/sec
sec-cos = 1/cos - cos = (1-cos^2)/cos csc^2 cos^ = (1/sin^2)cos^2 = cot^2 sin/csc = sin^2 and cos/sec = cos^2
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