Lesson 7

Workshop: Shapes Classification

Est. Class Sessions: 1

Daily Practice and Problems

Teacher Notes
X

TIMS Task

Your students may notice that one counterexample is enough to prove something false. Proving something true is harder, but a good demonstration shows understanding.

  1. No. Two right angles prevent a triangle being drawn. The shape would have to be at least 4-sided.
  2. No. It does not have to be equal. The third angle could be different, in which case the third side will be different, forming an isosceles triangle.
  3. No. Students should construct triangles with two equal sides and then determine if the angles are different.

V. Is It Possible

You may need to experiment to find these answers. Explain your answers in words or pictures.

  1. Can a triangle have two right angles?
  2. If two angles of a triangle are equal, does the third angle have to be equal to the other two angles?
  3. If a triangle has two equal sides, can its angles all be different sizes?