Question 1101708
{{{ 2sec^2(theta)tan^2(theta)-tan^4(theta)=sec^4(theta)-1 }}}
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Multiply thru by cos^2
{{{ 2tan^2(t)-sin^4(t)/cos^2(t) = sec^2(t)- cos^2(t) }}}
Multiply thru by cos^2 again
{{{ 2sin^2(t)-sin^4(t) = 1- cos^4(t) }}}
{{{ 2sin^2(t) - 1 = sin^4(t) - cos^4(t)}}}
{{{ 2sin^2(t) - 1 = (sin^2(t) - cos^2(t))*(sin^2(t) + cos^2(t))}}}
{{{ 2sin^2(t) - 1 = sin^2(t) - cos^2(t)}}}
{{{ 2sin^2(t) - sin^2(t) - cos^2(t) = sin^2(t) - cos^2(t)}}}
{{{sin^2(t) - cos^2(t) = sin^2(t) - cos^2(t)}}}