#sintheta-cot^2theta+tan^2theta#
#=sqrt(sin^2theta)-(cos^2theta)/sin^2theta+(sin^2theta)/cos^2theta#
#=sqrt(1-cos^2theta)-cos^2theta/(sqrt(1-cos^2theta))+(sqrt(1-cos^2theta))/cos^2theta#
#= sqrt(1-cos^2theta)+(1-cos^2theta-cos^4theta)/(cos^2thetasqrt(1-cos^2theta))#
#=(cos^2theta(1-cos^2theta)+1-cos^2theta-cos^4theta)/(cos^2thetasqrt(1-cos^2theta))#
#=(cancel(cos^2theta)-cos^4theta+1-cos^4thetacancel(-cos^2theta))/(cos^2thetasqrt(1-cos^2theta)#
#=(1-2cos^4theta)/(sqrt(cos^4theta-cos^6theta))#