Correct Answer - Option 2 :

\(\dfrac{3\pi}{4}\)
**Concept:**

The** interior angle** of a regular polygon is given by:

**\(\rm (n - 2) \times \frac{180^{\circ}}{n}\)**

Where, n = number of sides

Interior Angle = 180°- Exterior Angle

**Calculation:**

Regular Octagon has 8 sides

so, n = 8

Interior Angle

= \(\rm (n - 2) \times \frac{180^{\circ}}{n}\)

= \(\rm (8 - 2) \times \frac{180^{\circ}}{8}\)

= \(\rm 6 \times \frac{180^{\circ}}{8}\)

= \(\dfrac{3\pi}{4}\)