1+sec^2 x sin^2 x=sec^2 x
=1+(1/cos^2 x) sin^2 x = 1/cos^2x
=cos^2 x/cos^2 x + sin^2 x/cos^2 x = 1/cos^2 x
= (cos^2x+sin^2 x)/cos^2 x = 1/cos^2 x
multiply both sides by cos^2 x cos^2x + sin^2 x = 1
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