# Arc

• Oct 28th 2012, 02:32 PM
M670
Arc
The radius of the circle with a central angle of http://webwork.mathstat.concordia.ca...219fe87b11.png that intercepts an arc with length 9 miles is miles.

I came up with 2.02 miles
or 12.7 miles both seem wrong
but then if the formula is S=r(theta) and I would get 9=r(255) r=9/255 r=.035?
I am just not sure what to do?
• Oct 28th 2012, 02:38 PM
skeeter
Re: Arc
$s = r\theta$ is only valid if $\theta$ is in radians
• Oct 28th 2012, 02:42 PM
M670
Re: Arc
can't I convert it by multiplying (pi/180)
So it would be 255(pi/180)= 4.45 radians
• Oct 28th 2012, 02:44 PM
skeeter
Re: Arc
yes
• Oct 28th 2012, 02:45 PM
M670
Re: Arc
which would then be 9/4.45=2.02 miles as my radius
• Oct 28th 2012, 03:08 PM
skeeter
Re: Arc
Quote:

Originally Posted by M670
which would then be 9/4.45=2.02 miles as my radius

"seem wrong" now?
• Oct 28th 2012, 06:53 PM
M670
Re: Arc
Quote:

Originally Posted by skeeter
"seem wrong" now?

I really can't see my mistake... in this question
The process looks good to me, I convert 255 degrees into radians then use the formula to derive 2.02 miles as my radius
• Oct 28th 2012, 07:11 PM
Plato
Re: Arc
Quote:

Originally Posted by M670
I really can't see my mistake... in this question
The process looks good to me, I convert 255 degrees into radians then use the formula to derive 2.02 miles as my radius

I think people who still use degrees, get what they deserve.
Let $\theta=255\cdot\frac{\pi}{180}$ then $r=\frac{9}{\theta}$.
You should get $2.02220398281467$.