#cottheta+tan^3theta#
#=costheta/sintheta+sin^3theta/cos^3theta#
#=(cos^4theta+sin^4theta)/(sintheta*cos^3theta#
#=((cos^2theta+sin^2theta)^2-2sin^2thetacos^2theta)/(sintheta(1-sin^2theta)^(3/2)#
#=(1-2sin^2theta(1-sin^2theta))/(sintheta(1-sin^2theta)^(3/2)#