#cos theta/(1-sin theta) + cos theta/ (1+sin theta) = 4#
#(cos theta (1+sin theta)+cos theta(1-sin theta))/((1-sin theta)(1+sin theta)) =4#
#(cos theta + sin theta cos theta+ cos theta-sin theta cos theta)/(1-sin^2 theta)=4#
#(2cos theta)/cos^2 theta = 4#
#2/cos theta =4#
#2=4cos theta#
#1/2 = cos theta#
#theta = cos^-1 (1/2)#
#theta=+- 60 + 360^@n#