3Pi/2 is the official answer
x = 2, -2, -pi/2 pi/2 3pi/2
basically what ND did.
first to find possible solutions
squaring both sides, equating indices
(2x^2 - 10)|cos(x)| = |x| cos(x)
cos(x) = 0 solutions,
-pi/2, pi/2 3pi/2
else if cos(x) != 0
(2x^2 -10) = |x|...