standard_description: Tell and write time in hours and half-hours using analog and digital clocks.
problem_activity: Task
Consider a circle with center $O$ and let $P\,$ be a point on the circle. Suppose $L$ is a tangent line to the circle at $P$,  that is $L$  meets the circle only at $P$.
[IMG]
Show that $\overline{OP}\,$ is perpendicular to $L$.


aligns: no