Maths Olympiad Prep

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Geometry Difficulty 3.5 AMC 10/12 Find the answer Canada

In the diagram, point PP lies
inside square WXYZWXYZ so that PXY\triangle PXY is an equilateral
triangle.

The measure of WPZ\angle WPZ is

Pick one

Solution

In equilateral $\$\triangle
PXY,themeasureof, the measure of \angle
PXYis is 60°60\degreeand and PX=XY$.

In square WXYZWXYZ, the measure of
WXY\angle WXY is 90°90\degree and WX=XYWX=XY.

Therefore, $WXP=WXYPXY=90°60°=30°\$\angle WXP=\angle WXY-\angle PXY=90\degree-60\degree=30\degreeand and WX=PX$.

Thus WXP\triangle WXP is isosceles,
and so $PWX=WPX=180°30°2=75°$.\$\angle PWX=\angle WPX=\dfrac{180\degree-30\degree}{2}=75\degree\$.

The measure of PWZ\angle PWZ is $90°PWX=90°75°=15°$.\$90\degree-\angle PWX=90\degree-75\degree=15\degree\$.

In a similar way, we can show that $PZW=15°\$\angle PZW=15\degree,andso, and so WPZ=180°PWZ\angle WPZ=180\degree-\angle PWZ-\angle PZWor or WPZ=180°15°15°=150°$.\angle WPZ=180\degree-15\degree-15\degree=150\degree\$.

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Source: CEMC, University of Waterloo, licensed CC-BY-NC-4.0. Statement reproduced verbatim; metadata (topic, difficulty) added by this project.