A semicircular ring can be thought of simply as a ring divided equally into two parts. As the teacher taught, a ring is a figure made up of two concentric circles and the area between them. Therefore, the area of a semicircular ring is half that of a complete ring. The formula for the area of a semicircular ring is

So the formula for the area of a semicircular ring is S = 1/2π(R^2 – r^2), where R is the radius of the outer circle and r is the radius of the inner circle. The symbol π in the formula stands for the mathematical constant pi.

For example, if the radius of the outer circle is 10 and the radius of the inner circle is 5, then the area of the semicircle is 1/2π(10^2-5^2) = 1/2π(75) = 37.5π. Alternatively, if the radius of the outer circle is 6 and the radius of the inner circle is 3, then the area of the semicircle is 1/2π(6^2-3^2) = 1/2π(27) = 13.5π.

The content of this article must refer to: “The formula for the area of a ring” and “The formula for the area of a circle”.