Question 890004
{{{(1-cot^2(x))/(1+cot^2(x))=(1-cos^2(x)/sin^2(x))/(1+cos^2(x)/sin^2(x))}}}
.
.
{{{(1-cot^2(x))/(1+cot^2(x))=(sin^2(x)-cos^2(x))/(sin^2(x)+cos^2(x))}}}
.
.
{{{(1-cot^2(x))/(1+cot^2(x))=(sin^2(x)-cos^2(x))/(1)}}}
.
.
{{{(1-cot^2(x))/(1+cot^2(x))=(1-cos^2(x))-cos^2(x)}}}
.
.
{{{(1-cot^2(x))/(1+cot^2(x))=1-2cos^2(x)}}}
.
.
Not the same solution as you're looking for.