The angle which the normal to the line x – 3 y + 8 = 0 passing through the origin, makes with the positive x-axis is

We write the equation of the given line in the normal form as −12x+32y=82or xcos⁡α+ysin⁡α=p, where cos⁡α=−12, sin⁡α=32 and p=4,α  being the required angle ⇒α=120∘