I believe your mistake is that you are trying to use the sector area formula ti find arc length when there is already a formula for it.
The formula for it is
[tex]2r\pi( \frac{degree}{360} )[/tex]
So first substitute the values in and then simplify!
[tex]2(10.5)\pi( \frac{118}{360} )[/tex]
Now simplify!
21 × 118 is 2478 so it's
[tex] \frac{2478}{360} \pi[/tex]
When divided ou and multiplied, this is 21.62cm!
