#cos(theta) - tan(theta)*sec(theta)#
#=cos(theta) - sin(theta)/cos(theta) * 1/cos(theta)#
#=cos(theta) -sin(theta)/cos^2(theta)#
#=sqrt(1-sin^2(theta)) - sin(theta)/(1-sin^2(theta))#
#=((1-sin^2(theta))sqrt(1-sin^2(theta)) - sin(theta))/(1-sin^2(theta))#