Stage: 4 Challenge Level: 
A right-angled triangle ABC is right-angled at B.
An equilateral triangle is constructed on BC.
A line QD is drawn, where Q is the midpoint of AC.
Prove that AB // QD.
Congruence. Parallel lines. Right angled triangles. Inequality/inequalities. Generalising. Stage 5 - Reviewed 2012. Number theory. Manipulating algebraic expressions/formulae. Dynamical systems. Mathematical reasoning & proof.
Published September 2002.
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