The formula to measure the length of the arc is. Whenever you want to find the length of an arc of a circle a portion of the circumference you will use the arc length formula. If you need to find the area of a sector using the arc length that distance will be given to you.
If the central angle is measured in radians the formula instead becomes.
Area of semicircle area of quadrant Finding the area of a semicircle or quadrant should be a piece of cake now just think about what part of a circle they are. Pr2 frac text central angle in degrees 360 text degrees text sector area pr2 360 degreescentral angle in degrees. The Radius of a Sector Formula calculates the radius by dividing the length of an arc by the value of circumference of p. L th r when th is in radians L th p 180 r when th is in degrees.