Separate variables to get dy = 2sec2(3x)dx
Integrate both sides to get y = (2/3)tan(3x) + C
Since y = 3 when x = π/4, we have 3 = (2/3)tan(3π/4) + C
3 = (2/3)(-1) + C
C = 11/3
So, y = (2/3)tan(3x) + 11/3