mathematics 9 circle geometry
Specific Curriculum Outcome
M01 Students will be expected to solve problems and justify the solution strategy, using the following circle properties:
M01 Students will be expected to solve problems and justify the solution strategy, using the following circle properties:
 The perpendicular from the centre of a circle to a chord bisects the chord.
 The measure of the central angle is equal to twice the measure of the inscribed angle subtended by the same arc.
 The inscribed angles subtended by the same arc are congruent.
 A tangent to a circle is perpendicular to the radius at the point of tangency.
M01 activities

 Circle Definition from Annie Perkins (@Anniekperkins )  Draw an obviously not circle on the board and ask students why it's not a circle. Be very obstinate about not understanding what they meant by "your circle isn't perfectly curvy" etc. Keep pushing students thinking until you get to the idea of a circle as a set of point equidistant from the center.

 Freehand Circle Drawing Contest  Students take turns trying to draw the best freehand circle that they can on the whiteboard (1m in diameter in less than a second). How can they use the circle properties to judge who has made the most perfect circle? David Hax demonstrates how to draw a quick freehand circle on a sheet of paper.