### Home > CCG > Chapter Ch10 > Lesson 10.2.3 > Problem10-104

10-104.

The radian measure of a central angle of $90º$ is $\frac { \pi } { 2 }$. What must the radian measure of a central angle of $180º$ be? How can you tell without actually computing the radian measure?

Since the angle is doubled, the arc length must be doubled, and in turn, the ratio of arc length to radius, or radian measure, must also double and thus be $π$.