Question 1129815
{{{cos^2(a)-cot^2(a)/sin^2(a)-tan^2(a)}}}
= {{{cos^2(a)-(co2^2(a)/sin^2(a))/sin^2(a)-tan^2(a)}}}
= {{{cos^2(a)-cos^2(a)/sin^4(a)-tan^2(a)}}}