<?xml version="1.0" encoding="utf-8"?>
<!-- More Geometry Snacks #5 (What's the Angle?), drawn by hand as a ruler-and-compass construction.
     The base AB is fixed on the hidden points A and B. The apex P is the handle: it slides on a hidden track along the
     perpendicular bisector of AB, from the midpoint M (the triangle flat) to three sides above it, so the triangle
     stays isosceles (AP and PB carry one tick each). The square P B C D stands on the side PB, away from the triangle:
     perpendiculars to PB at B and at P, cut by circles of radius PB. The blue segment runs from A to D, the far top
     corner of the square, and the asked angle is at A between AB and AD. The handle starts with the apex two sides
     above the base, as the book draws it. -->
<Drawing Version="1">
  <Viewport Left="-0.6" Top="7.6" Right="8.6" Bottom="-0.8" />
  <Scene Left="-0.6" Top="7.6" Right="8.6" Bottom="-0.8" />
  <Styles>
    <PointStyle Name="Handle" Size="15" Fill="#FFFFFFFF" Color="#FF1E1E1E" StrokeWidth="2.5">
      <Dark Fill="#FF1E2228" Color="#FFF2F2F2" />
    </PointStyle>
    <ShapeStyle Name="Blue" Color="#FF0000FF" StrokeWidth="3" Fill="#FFB9B9FF">
      <Dark Color="#FF9DA3FF" Fill="#FF7F86D6" />
    </ShapeStyle>
    <LineStyle Name="BlueLine" Color="#FF0000FF" StrokeWidth="3">
      <Dark Color="#FF9DA3FF" />
    </LineStyle>
    <LineStyle Name="Ink" Color="#FF000000" StrokeWidth="3">
      <Dark Color="#FFE8EBF0" />
    </LineStyle>
    <ShapeStyle Name="Frame" Color="#FF000000" StrokeWidth="3" IsFilled="false">
      <Dark Color="#FFE8EBF0" />
    </ShapeStyle>
  </Styles>
  <Figures>
    <FreePoint Name="A" Visible="false" Locked="true" X="0" Y="0" />
    <FreePoint Name="B" Visible="false" Locked="true" X="2" Y="0" />
    <Segment Name="AB" Style="Ink">
      <Dependency Name="A" />
      <Dependency Name="B" />
    </Segment>
    <MidPoint Name="M" Visible="false">
      <Dependency Name="A" />
      <Dependency Name="B" />
    </MidPoint>
    <SegmentBisector Name="axis" Visible="false">
      <Dependency Name="A" />
      <Dependency Name="B" />
    </SegmentBisector>
    <!-- the track: three sides up the bisector from M -->
    <CircleByRadius Name="reach1" Visible="false">
      <Dependency Name="A" />
      <Dependency Name="B" />
      <Dependency Name="M" />
    </CircleByRadius>
    <IntersectionPoint Name="U1" Visible="false" Algorithm="IntersectLineAndEllipse1">
      <Dependency Name="axis" />
      <Dependency Name="reach1" />
    </IntersectionPoint>
    <CircleByRadius Name="reach2" Visible="false">
      <Dependency Name="A" />
      <Dependency Name="B" />
      <Dependency Name="U1" />
    </CircleByRadius>
    <IntersectionPoint Name="U2" Visible="false" Algorithm="IntersectLineAndEllipse1">
      <Dependency Name="axis" />
      <Dependency Name="reach2" />
    </IntersectionPoint>
    <CircleByRadius Name="reach3" Visible="false">
      <Dependency Name="A" />
      <Dependency Name="B" />
      <Dependency Name="U2" />
    </CircleByRadius>
    <IntersectionPoint Name="U3" Visible="false" Algorithm="IntersectLineAndEllipse1">
      <Dependency Name="axis" />
      <Dependency Name="reach3" />
    </IntersectionPoint>
    <Segment Name="track" Visible="false">
      <Dependency Name="M" />
      <Dependency Name="U3" />
    </Segment>
    <PointOnFigure Name="P" Style="Handle" X="1" Y="4" Parameter="0.6666666667">
      <Dependency Name="track" />
    </PointOnFigure>
    <Segment Name="AP" Style="Ink" Decoration="OneTick">
      <Dependency Name="A" />
      <Dependency Name="P" />
    </Segment>
    <Segment Name="PB" Style="Ink" Decoration="OneTick">
      <Dependency Name="P" />
      <Dependency Name="B" />
    </Segment>
    <PerpendicularLine Name="atB" Visible="false">
      <Dependency Name="PB" />
      <Dependency Name="B" />
    </PerpendicularLine>
    <Circle Name="aboutB" Visible="false">
      <Dependency Name="B" />
      <Dependency Name="P" />
    </Circle>
    <IntersectionPoint Name="C" Visible="false" Algorithm="IntersectLineAndEllipse1">
      <Dependency Name="atB" />
      <Dependency Name="aboutB" />
    </IntersectionPoint>
    <PerpendicularLine Name="atP" Visible="false">
      <Dependency Name="PB" />
      <Dependency Name="P" />
    </PerpendicularLine>
    <Circle Name="aboutP" Visible="false">
      <Dependency Name="P" />
      <Dependency Name="B" />
    </Circle>
    <IntersectionPoint Name="D" Visible="false" Algorithm="IntersectLineAndEllipse1">
      <Dependency Name="atP" />
      <Dependency Name="aboutP" />
    </IntersectionPoint>
    <Polygon Name="PBCD" Style="Frame">
      <Dependency Name="P" />
      <Dependency Name="B" />
      <Dependency Name="C" />
      <Dependency Name="D" />
    </Polygon>
    <Segment Name="AD" Style="BlueLine">
      <Dependency Name="A" />
      <Dependency Name="D" />
    </Segment>
    <AngleArc Name="asked" Style="Blue" Radius="40">
      <Dependency Name="A" />
      <Dependency Name="B" />
      <Dependency Name="D" />
    </AngleArc>
  </Figures>
</Drawing>
