Originally Posted by

**BobBali** Hi All,

The problem below shows a sector of a circle on the right hand side and when it is folded it makes the cone on the left. Find the arc length.

I started of by finding the slant height or radius:

$\displaystyle \sqrt{10^2 + 6^2} = 11.7$

To find arc length i have the formula:

$\displaystyle \frac{\theta}{360} \times 2\pi r$

But, How do i find the angle in the unfolded sector?

I tried finding the the angle of the top part of the cone using:

$\displaystyle tan\theta = \frac{6}{10} = 31 \times 2 = 62$

Then, 360 - 62 = 329 But, this input into the arc-length formula is not the

right answer.