Finding shaded area of circle

Question

How do I find the area of the shaded area if the circle's radii are 15cm and 13cm and the angle of the triangle in it is 80? 

 

What formulas do I have to use?

 

 

http://i.imgur.com/ULIRrdZ.jpg

Answer 1

find the area of the larger sector and subtract the area of the smaller sector and you get the shaded area

area of a sector: A=(q/360)(pi)(r^2) where q is 80º and r=13 and r=15

A=(80)/(360)(pi)(15^2)

A=(2/9)(pi)(225)

A=(2)(pi)(25) because 225/9=25

A=50(pi) for the area of the larger sector

 

A=(80/360)(pi)(13^2)

A=(2/9)(pi)(169)

A=(2)(pi)( 18 7/9) because 169/9=18 7/9

A=(37 5/9)(pi) for the smaller sector

subtract

A=(50)(pi)-(37 5/9)(pi)

A=12 4/9(pi)

A=12.4444444*3.14159

A=39.09534 square centimeters is the shaded area