Question 353494
Let {{{T=tan(x)}}},{{{ S=sec(x)}}}
{{{T^3S^2=(S^2-S^4)T}}}
{{{T^2=1-S^2}}}
By trignometric identity, 
{{{1+T^2=S^2}}}
{{{T^2=1-(1+T^2)}}}
{{{T^2=1-1-T^2}}}
{{{T^2=-T^2}}}
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