First of all, let's recall that the full circumference is

Now, since 30 is one twelfth of 360, a 30° arc will be one twelfth of the whole circumference. So, if you call the arc length A, you have

Since we know the arc length, we can build and solve the following equation:

Assuming you need the integral expressing the volume of

, the easiest setup is to integrate with respect to

first.
This is done with either


Thanks to symmetry, integrating with respect to either

or

first will be nearly identical.
First, with respect to

:


Next, with respec to

:

The correct answer is 0.2
The answer is B because the bottom has to be supplementary to 180 degrees because their supplementary angles
Answer: If four numbers are proportional, a : b = c : d, then the product of the extremes is equal to the product of the means. ad = bc