The diameter of a circle is 8 centimeters. A central angle of the circle of the circle intercepts an arc of 12 centimeters. What is the radian measure of the angle?

if the diameter is 8, that means the radius is half that, or 4, now the arc made by the central angle is 12 units, thus  [latex]\bf \textit{arc's length}\\\\ s=r\theta \qquad \begin{cases} r=radius\\ \theta =angle\ in\\ \qquad radians\\ ------\\ r=4\\ s=12 \end{cases}\implies 12=4\theta \implies \cfrac{12}{4}=\theta \implies \boxed{3=\theta }[/latex]