Activity 01
Paper Diagonal Split: Angle Sum Proof
Students draw various quadrilaterals on paper, draw one diagonal, cut along it to form two triangles, then arrange the triangles side-by-side to form a straight line. They measure the line's angle to verify 360 degrees. Pairs discuss why this works for any quadrilateral.
Explain why the sum of angles in a quadrilateral is 360 degrees.
Facilitation TipDuring Paper Diagonal Split, circulate with scissors and protractors to ensure students cut precisely along the diagonal to confirm the angle sum visually.
What to look forProvide students with a quadrilateral where three angles are given (e.g., 80°, 100°, 70°). Ask them to calculate the missing fourth angle and state the type of quadrilateral if possible. Include a question: 'What is the sum of the angles you calculated?'