1. The problem asks for the radian measure of angle $\angle A$ in a circle with radius 3, where the angle is marked as $\pi$ radians. 2. The radian measure of an angle in a circle is the length of the arc subtended by the angle divided by the radius of the circle. 3. Here, the angle $\angle A$ is already given as $\pi$ radians, which means the measure of $\angle A$ is $\pi$. 4. Therefore, the radian measure of $\angle A$ is simply: $$m\angle A = \pi$$ This is the final answer.