Things You'll Need
Instructions
Obtain the constant "pi" with the required precision (see References). The pi value rounded to thousands (3.142) is typically sufficient.
Divide the sector angle by 360, and then multiply the result by the constant pi. For example, if the sector angle is 30 degrees, then (30 / 360) x 3.142 = 0.262.
Raise the radius of the circle to the square. For example, if the radius is 3 inches, then 3 x 3 = 9 square inches.
Multiply the values obtained in steps 2 and 3 to calculate the area of the sector. In our example, the sector area is 0.262 x 9 square inches = 2.358 square inches.