Given:
Length of arc AB is 4 units.
The measure of central angle corresponding to arc AB is 30 degrees.
To find:
The circumference of the circle.
Solution:
The formula for arc length is:
![s=2\pi r(\theta )/(360^\circ)](https://img.qammunity.org/2022/formulas/mathematics/high-school/zcnjr1b095bxr9uwzwvewewivm23946unx.png)
Where, r is the radius and
is the central angle.
It is also written as:
![s=C(\theta )/(360^\circ)](https://img.qammunity.org/2022/formulas/mathematics/high-school/eq14e1gzc1gon47l072cx0psv0c7twjxw6.png)
Where, C is the circumference of the circle.
Putting
in the above formula, we get
![4=C(30^\circ)/(360^\circ)](https://img.qammunity.org/2022/formulas/mathematics/high-school/58ged855h067o8v3iih5t6ywheugps4z7b.png)
![4=(1)/(12)C](https://img.qammunity.org/2022/formulas/mathematics/high-school/ri22604rpqas1u9lhvyrfik14nh47qz6kl.png)
Multiply both sides by 12.
![4* 12=C](https://img.qammunity.org/2022/formulas/mathematics/high-school/sty3rrm9dxlnnlrrpk87ik5nmvh8lsizxi.png)
![48=C](https://img.qammunity.org/2022/formulas/mathematics/high-school/yk6bktq0fdvvtybbb6s924l078nic7y4en.png)
The circumference of the circle is 48 units.
Therefore, the correct option is A.