standard_description: Use geometric descriptions of rigid motions to transform figures and to predict the effect of a given rigid motion on a given figure; given two figures, use the definition of congruence in terms of rigid motions to decide if they are congruent.
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