Stage: 5 Challenge Level: 
| $P$ is a point inside a square $ABCD$ such that $PA= 1$, $PB = 2$ and $PC = 3$. How big is ${\angle APB} $ ? |
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Cartesian equations of circles. Pythagoras' theorem. Stage 5 - Reviewed 2012. Cosine rule. Sine rule. Long problems. Circles. Similarity. Stage 5 needs dealing with. Perpendicular lines. Angles.
Published March 2002.
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