Angle to Chord

Weekly Problem 23 - 2008
A triangle has been drawn inside this circle. Can you find the length of the chord it forms?
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$P$, $Q$ and $R$ are points on the circumference of a circle of radius 4cm. $\angle PQR=45^o$. What is the length of chord $PR$?

 

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Angle to Chord

If you liked this problem, here is an NRICH task which challenges you to use similar mathematical ideas.