Replace sec^2 with 1+tan^2 and solve the resulting quadratic.
.. tan(x)^2 +4 = 2(1 +tan(x)^2) +tan(x)
.. 0 = tan(x)^2 +tan(x) -2
.. (tan(x) -1)*(tan(x) +2) = 0
From the zero-product rule
.. tan(x) -1 = 0 . . . . . has solutions x = {π/4, 5π/4}
.. tan(x) +2 = 0 . . . . has solutions x = {arctan(-2)+π, arctan(-2) +2π}
