(b)The sum of interior angles of a regular polygon is . Find the number of sides of the regular polygon.[2]?

To find the number of sides of a regular polygon, we can use the formula for the sum of interior angles of a polygon:

Sum of interior angles = (n-2) * 180 degrees

Given that the sum of interior angles is 1260 degrees, we can set up the equation:

1260 = (n-2) * 180

Solving for n:

1260 = 180n - 360
1260 + 360 = 180n
1620 = 180n
n = 1620 / 180
n = 9

Therefore, the regular polygon has 9 sides.