Converting a Red-Shaded Circle Diagram to Fraction Notation

To solve this problem, we need to determine the fraction represented by the shaded area of a circle.

The diagram shows a circle divided into two equal parts. One of these parts is shaded.

Fractions are expressed as the part over the whole. Here, the shaded section represents one part, while the total sections are two. Therefore, the fraction representing the shaded portion is $\frac{1}{2}$.

Therefore, the solution to the problem is $\frac{1}{2}$.