<?xml version="1.0" encoding="utf-8"?>
<!-- Geometry Snacks #14 (What's the Angle?), drawn by hand as a ruler-and-compass construction.
     The 70° at A and the 80° at B cannot be constructed, so they are laid out by hidden base points: A and B are the
     bottom corners, C is the upper right corner (on the ray at 80° from B), and the handle D slides along a hidden
     stretch of the ray at 70° from A, from 3.4 to 9 times an eighth of the bottom side, starting where the book has it.
     The bisectors of the angles at D and C meet at P; the asked angle is at P, between the bisectors. Each bisected angle
     is marked by its two halves in grey, one arc at D and two at C, where the book puts tick marks on the arcs. The
     70° and 80° labels hang on points of the bisectors at A and B, a quarter of AB from the corner, in a style that
     draws nothing. The angle at P is 75° wherever D is, since the halves of the angles at C and D add up to 105°. -->
<Drawing Version="1">
  <Viewport Left="-0.9" Top="9.5" Right="8.9" Bottom="-0.6" />
  <Scene Left="-0.9" Top="9.5" Right="8.9" Bottom="-0.6" />
  <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>
    <TextStyle Name="Mark" FontSize="28" Color="#FF000000" FontFamily="Segoe UI" Bold="true">
      <Dark Color="#FFE8EBF0" />
    </TextStyle>
    <PointStyle Name="Anchor" Size="1" Fill="#00000000" Color="#00000000" StrokeWidth="0" />
  </Styles>
  <Figures>
    <FreePoint Name="A" Visible="false" Locked="true" X="0" Y="0" />
    <FreePoint Name="B" Visible="false" Locked="true" X="7.9562" Y="0.8362" />
    <FreePoint Name="C" Visible="false" Locked="true" X="6.2332" Y="6.8439" />
    <FreePoint Name="Dnear" Visible="false" Locked="true" X="0.8225" Y="3.2990" />
    <FreePoint Name="Dfar" Visible="false" Locked="true" X="2.1773" Y="8.7327" />
    <Segment Name="Slide" Visible="false">
      <Dependency Name="Dnear" />
      <Dependency Name="Dfar" />
    </Segment>
    <PointOnFigure Name="D" Style="Handle" X="1.0161" Y="4.0753" Parameter="0.142857">
      <Dependency Name="Slide" />
    </PointOnFigure>
    <AngleBisector Name="bisectorD" Visible="false">
      <Dependency Name="D" />
      <Dependency Name="A" />
      <Dependency Name="C" />
    </AngleBisector>
    <AngleBisector Name="bisectorC" Visible="false">
      <Dependency Name="C" />
      <Dependency Name="D" />
      <Dependency Name="B" />
    </AngleBisector>
    <IntersectionPoint Name="P" Visible="false" Algorithm="IntersectLineAndLine">
      <Dependency Name="bisectorD" />
      <Dependency Name="bisectorC" />
    </IntersectionPoint>
    <Polygon Name="ABCD" Style="Frame">
      <Dependency Name="A" />
      <Dependency Name="B" />
      <Dependency Name="C" />
      <Dependency Name="D" />
    </Polygon>
    <AngleArc Name="halfD1" Style="Grey" Radius="45">
      <Dependency Name="D" />
      <Dependency Name="A" />
      <Dependency Name="P" />
    </AngleArc>
    <AngleArc Name="halfD2" Style="Grey" Radius="45">
      <Dependency Name="D" />
      <Dependency Name="P" />
      <Dependency Name="C" />
    </AngleArc>
    <AngleArc Name="halfC1" Style="Grey" Radius="45" Arcs="2">
      <Dependency Name="C" />
      <Dependency Name="D" />
      <Dependency Name="P" />
    </AngleArc>
    <AngleArc Name="halfC2" Style="Grey" Radius="45" Arcs="2">
      <Dependency Name="C" />
      <Dependency Name="P" />
      <Dependency Name="B" />
    </AngleArc>
    <Segment Name="DP" Style="Ink">
      <Dependency Name="D" />
      <Dependency Name="P" />
    </Segment>
    <Segment Name="CP" Style="Ink">
      <Dependency Name="C" />
      <Dependency Name="P" />
    </Segment>
    <AngleArc Name="asked" Style="RedMark" Radius="40">
      <Dependency Name="P" />
      <Dependency Name="D" />
      <Dependency Name="C" />
    </AngleArc>
    <AngleArc Name="givenA" Style="Ink" Radius="40">
      <Dependency Name="A" />
      <Dependency Name="B" />
      <Dependency Name="D" />
    </AngleArc>
    <AngleArc Name="givenB" Style="Ink" Radius="40">
      <Dependency Name="B" />
      <Dependency Name="C" />
      <Dependency Name="A" />
    </AngleArc>
    <!-- the labels: on the bisectors at A and B, a quarter of AB from the corner -->
    <MidPoint Name="Half" Visible="false">
      <Dependency Name="A" />
      <Dependency Name="B" />
    </MidPoint>
    <MidPoint Name="Quarter" Visible="false">
      <Dependency Name="A" />
      <Dependency Name="Half" />
    </MidPoint>
    <AngleBisector Name="bisectorA" Visible="false">
      <Dependency Name="A" />
      <Dependency Name="B" />
      <Dependency Name="D" />
    </AngleBisector>
    <AngleBisector Name="bisectorB" Visible="false">
      <Dependency Name="B" />
      <Dependency Name="C" />
      <Dependency Name="A" />
    </AngleBisector>
    <CircleByRadius Name="reachA" Visible="false">
      <Dependency Name="A" />
      <Dependency Name="Quarter" />
      <Dependency Name="A" />
    </CircleByRadius>
    <CircleByRadius Name="reachB" Visible="false">
      <Dependency Name="A" />
      <Dependency Name="Quarter" />
      <Dependency Name="B" />
    </CircleByRadius>
    <IntersectionPoint Name="AtA" Style="Anchor" Algorithm="IntersectLineAndEllipse2">
      <Dependency Name="bisectorA" />
      <Dependency Name="reachA" />
    </IntersectionPoint>
    <IntersectionPoint Name="AtB" Style="Anchor" Algorithm="IntersectLineAndEllipse2">
      <Dependency Name="bisectorB" />
      <Dependency Name="reachB" />
    </IntersectionPoint>
    <AttachedLabel Name="LabelA" Style="Mark" Z="1" OffsetX="-24" OffsetY="-19" Text="70°">
      <Dependency Name="AtA" />
    </AttachedLabel>
    <AttachedLabel Name="LabelB" Style="Mark" Z="1" OffsetX="-24" OffsetY="-19" Text="80°">
      <Dependency Name="AtB" />
    </AttachedLabel>
  </Figures>
</Drawing>
