In terms of sine and cosine, the right side is
... 1/sin(x)² - cos(x)²/sin(x)²
... = (1-cos²(x))/sin²(x)
... = sin²(x)/sin²(x) = 1
Then the equation becomes
... 3tan²(x) -2 = 1
... 3tan²(x) = 3
... tan(x) = ±√(3/3) = ±1
In the given range, the solutions are x = {pi/4, 3pi/4}.