Mark M. answered 01/10/19
Retired math prof. Calc 1, 2 and AP Calculus tutoring experience.
Parallel lines have the same slope.
slope of y = (4/3)(x + π) is 4/3.
Slope of tangent line to the curve y = tanx at (x, tanx) is y'.
y' = sec2x
So, sec2x = 4/3.
Therefore, cos2x = 3/4
So, cosx = ±√3/2
Solutions in the interval (0, π): x = π/6, 5π/6