<?xml version="1.0" encoding="utf-8"?>
<!-- Geometry Snacks #16 (What's the Angle?), drawn by hand as a ruler-and-compass construction.
     The middle triangle LTR stands on the hidden base points L and R; its apex T is the handle, free inside a hidden
     rectangle above LR, starting where the book has it. The equilateral triangles are built outward on LT and TR by
     circles of the sides' radius about their ends (E on the left, F on the right), shaded grey. The lines ER and FL cross
     at X; the asked angle is at X, the one opening down toward LR. It is 120° wherever T is: the triangles LTF and ETR
     are the same triangle turned 60° about T. -->
<Drawing Version="1">
  <Viewport Left="-3.2" Top="6" Right="7.2" Bottom="-2" />
  <Scene Left="-3.2" Top="6" Right="7.2" Bottom="-2" />
  <Styles>
    <PointStyle Name="Handle" Size="15" Fill="#FFFFFFFF" Color="#FF1E1E1E" StrokeWidth="2.5">
      <Dark Fill="#FF1E2228" Color="#FFF2F2F2" />
    </PointStyle>
    <ShapeStyle Name="Frame" Color="#FF000000" StrokeWidth="3" IsFilled="false">
      <Dark Color="#FFE8EBF0" />
    </ShapeStyle>
    <LineStyle Name="Ink" Color="#FF000000" StrokeWidth="3">
      <Dark Color="#FFE8EBF0" />
    </LineStyle>
    <ShapeStyle Name="Grey" Color="#FF000000" StrokeWidth="3" Fill="#FFC8C8C8">
      <Dark Color="#FFE8EBF0" Fill="#FF6B7280" />
    </ShapeStyle>
    <ShapeStyle Name="RedMark" Color="#FFEF303F" StrokeWidth="3" Fill="#FFEF303F">
      <Dark Color="#FFD9333F" Fill="#FFD9333F" />
    </ShapeStyle>
  </Styles>
  <Figures>
    <FreePoint Name="L" Visible="false" Locked="true" X="0" Y="0" />
    <FreePoint Name="R" Visible="false" Locked="true" X="4" Y="0" />
    <FreePoint Name="R1" Visible="false" Locked="true" X="0.8" Y="1.5" />
    <FreePoint Name="R2" Visible="false" Locked="true" X="3.2" Y="1.5" />
    <FreePoint Name="R3" Visible="false" Locked="true" X="3.2" Y="3.5" />
    <FreePoint Name="R4" Visible="false" Locked="true" X="0.8" Y="3.5" />
    <Polygon Name="Room" Visible="false">
      <Dependency Name="R1" />
      <Dependency Name="R2" />
      <Dependency Name="R3" />
      <Dependency Name="R4" />
    </Polygon>
    <PointInRegion Name="T" Style="Handle" X="2.63" Y="2.68">
      <Dependency Name="Room" />
    </PointInRegion>
    <Circle Name="cL" Visible="false">
      <Dependency Name="L" />
      <Dependency Name="T" />
    </Circle>
    <Circle Name="cTL" Visible="false">
      <Dependency Name="T" />
      <Dependency Name="L" />
    </Circle>
    <IntersectionPoint Name="E" Visible="false" Algorithm="IntersectCircleAndCircle2">
      <Dependency Name="cL" />
      <Dependency Name="cTL" />
    </IntersectionPoint>
    <Circle Name="cR" Visible="false">
      <Dependency Name="R" />
      <Dependency Name="T" />
    </Circle>
    <Circle Name="cTR" Visible="false">
      <Dependency Name="T" />
      <Dependency Name="R" />
    </Circle>
    <IntersectionPoint Name="F" Visible="false" Algorithm="IntersectCircleAndCircle1">
      <Dependency Name="cR" />
      <Dependency Name="cTR" />
    </IntersectionPoint>
    <Polygon Name="LET" Style="Grey">
      <Dependency Name="L" />
      <Dependency Name="E" />
      <Dependency Name="T" />
    </Polygon>
    <Polygon Name="TFR" Style="Grey">
      <Dependency Name="T" />
      <Dependency Name="F" />
      <Dependency Name="R" />
    </Polygon>
    <Polygon Name="LTR" Style="Frame">
      <Dependency Name="L" />
      <Dependency Name="T" />
      <Dependency Name="R" />
    </Polygon>
    <Segment Name="ER" Style="Ink">
      <Dependency Name="E" />
      <Dependency Name="R" />
    </Segment>
    <Segment Name="FL" Style="Ink">
      <Dependency Name="F" />
      <Dependency Name="L" />
    </Segment>
    <IntersectionPoint Name="X" Visible="false" Algorithm="IntersectLineAndLine">
      <Dependency Name="ER" />
      <Dependency Name="FL" />
    </IntersectionPoint>
    <AngleArc Name="asked" Style="RedMark" Radius="40">
      <Dependency Name="X" />
      <Dependency Name="L" />
      <Dependency Name="R" />
    </AngleArc>
  </Figures>
</Drawing>
