# Math Help - Measure of central angle

1. ## Measure of central angle

A circle has radius of 7cm. How many degrees is the central angle subtended by an arc of length 5.5 cm?

can anybody help me what this problem all about... I can't understand the problem... Please do illustrate.

thanks

2. ## Re: Measure of central angle

Hey rcs.

For this you should use the standard arc-length formula which is arc-length = r*theta where r is the radius and theta is the angle sub-tended.

Arc (geometry) - Wikipedia, the free encyclopedia

3. ## Re: Measure of central angle

Originally Posted by chiro
Hey rcs.

For this you should use the standard arc-length formula which is arc-length = r*theta where r is the radius and theta is the angle sub-tended.

Arc (geometry) - Wikipedia, the free encyclopedia

I got
Theta = 5.5/7 = .7857... I think it is not right

4. ## Re: Measure of central angle

That is right of the angle is in radians.

In degrees we get:

> 5.5/7
[1] 0.7857143
> 5.5/7*180/pi
[1] 45.01811

or roughly 45 degrees.