Angles, triangles and circles
Build a model, justify why it applies and check the result.
IKMC Grades 9-10 - Selected Topics
Use the facts that angles on a straight line sum to 180° and angles around a point sum to 360°, adding only angles that do not overlap.
Apply the triangle angle sum and the exterior-angle property, and explain why they hold.
Explain why an angle bisector halves the angle but not, in general, the opposite side.
Split a polygon into triangles from one vertex and derive its interior-angle sum.