Lesson 8-6 Areas of different sections of a circle

A sector of a circle is the region between two radii and an arc of the circle. r a r = Sector of a circle Area of a circle

Example: Find the area of sector ABS 100  6cm B A S

- A segment of a circle is the region between a chord and an arc of the circle. r a h b r a h b = Segment of a circle

Example: Find the area of the segment m  ABC = 90° C B A A segment = A sector CBA – A ΔCBA = (mCA)/360  r 2 - ½bh = (90)/360  (10) 2 - ½(10)(10) 10cm = 78.5 – 50 = 28.5cm 2 A segment = 28.5cm 2

An annulus is the region between two concentric circles. r R annulus R r - =

Example: Find the annulus 12 cm 7 cm