Formula for the area of a circle

The cicrcumference of a circle is give by the formula C = pid where d is the diameter of the circle. The formula for the area of a circle is A = pir^2 . If the area of the circle is 9pi , what is the circumference of the circle ?

Write the formula for area of a circle.

Write the formula for the area of a sector of angle theta (in degrees) of a circle of radius r .

Write the formula for the area of a sector of angle theta (in degrees) of a circle of radius r .

Write the formula for the area of a segment in a circle a circle of radius r given that the sector angle is theta (in degrees).

Write the formula for the area of a segment in a circle of radius r given that the sector angle is theta (in degrees).

The radius of a circle is 14 cm. Find the radius of the circle whose area is double of the area of the circle.

The radius of a circle is 14cm. Find the radius of the circle whose area is double of the area of the circle.

Mention the formula to calculate area of a circle?