Mark M. answered 04/30/20
Retired Math prof with teaching and tutoring experience in trig.
6sin2x + sin(2x)secx - 6 = 0
6sin2x - 2sinxcosx(1/cosx) - 6 = 0
6sin2x - 2sinx - 6 = 0
3sin2x - sinx - 3 = 0
sinx = [1 ± √37] / 6
sinx = 1.18 or -0.8471
Since sinx can't be bigger than 1, we have sinx = -0.8471
x = Sin-1(0.8471) + π or 2π - Sin-1(0.8471) = 4.1521 or 5.2727