Stage: 4 Challenge Level: 
Draw some squares and draw in a diagonal plus two lines joining one of the other two vertices to the midpoint of the opposite sides.
What do you notice?
Would this work with a rectangle, a parallelogram, a trapezium?
Inequality/inequalities. Squares. Number theory. Similarity. Manipulating algebraic expressions/formulae. Stage 5 - Reviewed 2012. Generalising. Mathematical reasoning & proof. Dynamical systems. Straight edge & compass constructions.
Published November 2000,June 2009.
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