cos^x+1=3sinx*cosx
cos^2 x+1=3sinx*cosx
cos^2 x+sin^2 x +cos^2 x -3sinx*cosx = 0
2cos^2 x+sin^2 x -3sinx*cosx = 0 : cos^2 x не равно 0
2+tg^2 x — 3 tg x =0
tg x =t
t^2-3t+2=0
t1= 1; tg x = 1
t2 = 2; tg x = 2
x1 = arctg 1 + Pi n; x1 = Pi/4 + Pi n
x2 = arctg 2 +Pi k
Ответ: x1 = Pi/4 + Pi n