standard_description: Know precise definitions of angle, circle, perpendicular line, parallel line, and line segment, based on the undefined notions of point, line, distance along a line, and distance around a circular arc.
problem_activity: Task
What is the last digit of $7^{2011}$?  Explain.
What are the last  two  digits of $7^{2011}$?  Explain.


aligns: no