(tg+5)/2=1/(cos^2 x)
(tgx + 5)/2= 1+tg^2x tgx +5= 2+2 tg^2x 2tg^2x-tgx-3=0 1. tgx= -1 x= - pi/4+pi*k 2. tgx= 3/2 x= arctg (3/2) +pi*k