<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta name="aspect-ratio" content="1:1">
  <style>
    * { box-sizing: border-box; margin: 0; padding: 0; }
    body {
      font-family: system-ui, -apple-system, sans-serif;
      background: transparent;
      color: #1e2945;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      width: 100%;
      min-height: 100%;
      padding: 12px;
      user-select: none;
    }

    .toolbar {
      display: flex;
      gap: 8px;
      margin-bottom: 12px;
      z-index: 10;
    }

    .btn {
      padding: 6px 14px;
      font-size: 13px;
      font-weight: 600;
      border-radius: 20px;
      border: 1px solid #cbd5e1;
      background: #ffffff;
      color: #475569;
      cursor: pointer;
      transition: all 0.2s ease;
    }

    .btn.active[data-target="all"] {
      background: #1e2945;
      color: #ffffff;
      border-color: #1e2945;
    }

    .btn.active[data-target="diameter"] {
      background: #0284c7;
      color: #ffffff;
      border-color: #0284c7;
    }

    .btn.active[data-target="chord"] {
      background: #9333ea;
      color: #ffffff;
      border-color: #9333ea;
    }

    .svg-container {
      width: 100%;
      max-width: 380px;
      aspect-ratio: 1 / 1;
      position: relative;
    }

    svg {
      width: 100%;
      height: 100%;
      overflow: visible;
    }

    .line-seg {
      transition: opacity 0.3s ease, stroke-width 0.3s ease;
    }

    .dimmed {
      opacity: 0.15 !important;
    }

    .highlighted {
      stroke-width: 5.5px !important;
    }

    text {
      font-family: inherit;
      font-size: 13px;
      font-weight: 600;
      user-select: none;
      transition: opacity 0.3s ease;
    }

    .tag-bg {
      rx: 6px;
      transition: opacity 0.3s ease;
    }
  </style>
</head>
<body>

  <div class="toolbar">
    <button class="btn active" data-target="all">Both</button>
    <button class="btn" data-target="diameter">Diameter PQ</button>
    <button class="btn" data-target="chord">Chord XY</button>
  </div>

  <div class="svg-container">
    <svg viewBox="0 0 400 400">
      
      <circle cx="200" cy="200" r="150" fill="#f8fafc" stroke="#cbd5e1" stroke-width="3" />

      
      <circle cx="200" cy="200" r="5" fill="#1e2945" />
      <text x="200" y="222" text-anchor="middle" fill="#1e2945" font-size="14">O</text>

      
      <g id="grp-chord">
        <line class="line-seg" x1="85" y1="103" x2="330" y2="114" stroke="#9333ea" stroke-width="4" stroke-linecap="round" />
        
        <circle cx="85" cy="103" r="5.5" fill="#9333ea" />
        <circle cx="330" cy="114" r="5.5" fill="#9333ea" />

        <text x="70" y="100" text-anchor="end" fill="#9333ea" font-weight="700">X</text>
        <text x="345" y="112" text-anchor="start" fill="#9333ea" font-weight="700">Y</text>

        
        <rect class="tag-bg" x="110" y="60" width="180" height="26" fill="#f3e8ff" stroke="#d8b4fe" stroke-width="1" />
        <text x="200" y="77" text-anchor="middle" fill="#7e22ce" font-size="12">Chord XY (off center)</text>
      </g>

      
      <g id="grp-diameter">
        <line class="line-seg" x1="59" y1="251" x2="341" y2="149" stroke="#0284c7" stroke-width="4" stroke-linecap="round" />

        <circle cx="59" cy="251" r="5.5" fill="#0284c7" />
        <circle cx="341" cy="149" r="5.5" fill="#0284c7" />

        <text x="44" y="266" text-anchor="end" fill="#0284c7" font-weight="700">P</text>
        <text x="355" y="148" text-anchor="start" fill="#0284c7" font-weight="700">Q</text>

        
        <rect class="tag-bg" x="80" y="285" width="240" height="26" fill="#e0f2fe" stroke="#7dd3fc" stroke-width="1" />
        <text x="200" y="302" text-anchor="middle" fill="#0369a1" font-size="12">Diameter PQ (longest chord)</text>
      </g>
    </svg>
  </div>

  <script>
    const btns = document.querySelectorAll('.btn');
    const grpDiameter = document.getElementById('grp-diameter');
    const grpChord = document.getElementById('grp-chord');

    function setView(target) {
      btns.forEach(b => b.classList.toggle('active', b.dataset.target === target));

      if (target === 'all') {
        grpDiameter.classList.remove('dimmed');
        grpChord.classList.remove('dimmed');
        grpDiameter.querySelector('.line-seg').classList.remove('highlighted');
        grpChord.querySelector('.line-seg').classList.remove('highlighted');
      } else if (target === 'diameter') {
        grpDiameter.classList.remove('dimmed');
        grpDiameter.querySelector('.line-seg').classList.add('highlighted');
        grpChord.classList.add('dimmed');
        grpChord.querySelector('.line-seg').classList.remove('highlighted');
      } else if (target === 'chord') {
        grpChord.classList.remove('dimmed');
        grpChord.querySelector('.line-seg').classList.add('highlighted');
        grpDiameter.classList.add('dimmed');
        grpDiameter.querySelector('.line-seg').classList.remove('highlighted');
      }
    }

    btns.forEach(btn => {
      btn.addEventListener('click', () => setView(btn.dataset.target));
    });

    grpDiameter.addEventListener('click', () => setView('diameter'));
    grpChord.addEventListener('click', () => setView('chord'));
    grpDiameter.style.cursor = 'pointer';
    grpChord.style.cursor = 'pointer';
  </script>
</body>
</html>

Parts of a Circle: Radius, Diameter, Chord, and Sector

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta name="aspect-ratio" content="4:3">
  <style>
    * { box-sizing: border-box; margin: 0; padding: 0; }
    body {
      font-family: system-ui, -apple-system, sans-serif;
      background: transparent;
      color: #1e2945;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      min-height: 100%;
      padding: 10px;
      user-select: none;
    }
    .controls {
      display: flex;
      gap: 8px;
      margin-bottom: 8px;
    }
    .btn {
      font-size: 13px;
      font-weight: 600;
      padding: 6px 14px;
      border-radius: 20px;
      border: 1px solid #cbd5e1;
      background: #ffffff;
      color: #475569;
      cursor: pointer;
      box-shadow: 0 1px 2px rgba(0,0,0,0.05);
      transition: all 0.2s ease;
    }
    .btn.active {
      background: #0284c7;
      color: #ffffff;
      border-color: #0284c7;
    }
    .svg-container {
      width: 100%;
      max-width: 440px;
      height: auto;
    }
    svg {
      width: 100%;
      height: auto;
      display: block;
      overflow: visible;
    }
    .sector-shape {
      transition: opacity 0.3s ease, fill 0.3s ease;
    }
    .arc-path {
      transition: opacity 0.3s ease, stroke-width 0.3s ease;
    }
    .dimmed {
      opacity: 0.18 !important;
    }
    .highlight-sector {
      fill: #fcd34d !important;
    }
  </style>
</head>
<body>

  <div class="controls">
    <button class="btn active" id="btn-all" onclick="setMode('all')">Show Both</button>
    <button class="btn" id="btn-sector" onclick="setMode('sector')">Sector (Area)</button>
    <button class="btn" id="btn-arc" onclick="setMode('arc')">Arc (Edge)</button>
  </div>

  <div class="svg-container">
    <svg viewBox="0 0 440 330" aria-label="Circle diagram of sector and arc">
      <defs>
        
        <marker id="arrow-teal" viewBox="0 0 10 10" refX="6" refY="5" markerWidth="6" markerHeight="6" orient="auto-start-reverse">
          <path d="M 0 1 L 8 5 L 0 9 z" fill="#0d9488" />
        </marker>
        <marker id="arrow-amber" viewBox="0 0 10 10" refX="6" refY="5" markerWidth="6" markerHeight="6" orient="auto-start-reverse">
          <path d="M 0 1 L 8 5 L 0 9 z" fill="#d97706" />
        </marker>
      </defs>

      
      <circle cx="190" cy="165" r="115" fill="none" stroke="#cbd5e1" stroke-width="2" stroke-dasharray="5 4" />

      
      <g id="sector-group">
        <path class="sector-shape"
              d="M 190 165 L 256.0 70.8 A 115 115 0 0 1 278.1 238.9 Z"
              fill="#fef08a"
              stroke="#f59e0b"
              stroke-width="2" />
        
        
        <text x="282" y="152" fill="#b45309" font-size="14" font-weight="700">Sector</text>
        <text x="282" y="169" fill="#78350f" font-size="12" font-weight="600">(2D Area)</text>
        <line x1="278" y1="158" x2="238" y2="158" stroke="#d97706" stroke-width="1.5" marker-end="url(#arrow-amber)" />
      </g>

      
      <g id="radii-group">
        
        <line x1="190" y1="165" x2="256.0" y2="70.8" stroke="#d97706" stroke-width="2.5" stroke-linecap="round" />
        <text x="204" y="106" fill="#b45309" font-size="12" font-weight="600" transform="rotate(-55 204 106)">Radius</text>
        
        
        <line x1="190" y1="165" x2="278.1" y2="238.9" stroke="#d97706" stroke-width="2.5" stroke-linecap="round" />
        <text x="220" y="218" fill="#b45309" font-size="12" font-weight="600" transform="rotate(40 220 218)">Radius</text>
      </g>

      
      <g id="arc-group">
        <path class="arc-path"
              d="M 256.0 70.8 A 115 115 0 0 1 278.1 238.9"
              fill="none"
              stroke="#0d9488"
              stroke-width="5.5"
              stroke-linecap="round" />
        
        
        <text x="318" y="96" fill="#0f766e" font-size="14" font-weight="700">Arc AB</text>
        <text x="318" y="113" fill="#115e59" font-size="12" font-weight="600">(Curved Edge)</text>
        <path d="M 314 102 Q 295 106 280 115" fill="none" stroke="#0d9488" stroke-width="1.5" marker-end="url(#arrow-teal)" />
      </g>

      
      <circle cx="190" cy="165" r="4.5" fill="#1e2945" />
      <text x="175" y="170" fill="#1e2945" font-size="15" font-weight="700" text-anchor="end">O</text>

      
      <circle cx="256.0" cy="70.8" r="4" fill="#0f766e" />
      <text x="264" y="64" fill="#0f766e" font-size="14" font-weight="700">A</text>

      
      <circle cx="278.1" cy="238.9" r="4" fill="#0f766e" />
      <text x="286" y="254" fill="#0f766e" font-size="14" font-weight="700">B</text>
    </svg>
  </div>

  <script>
    function setMode(mode) {
      document.querySelectorAll('.btn').forEach(b => b.classList.remove('active'));
      document.getElementById('btn-' + mode).classList.add('active');

      const sector = document.getElementById('sector-group');
      const arc = document.getElementById('arc-group');
      const radii = document.getElementById('radii-group');

      if (mode === 'all') {
        sector.classList.remove('dimmed');
        arc.classList.remove('dimmed');
        radii.classList.remove('dimmed');
      } else if (mode === 'sector') {
        sector.classList.remove('dimmed');
        radii.classList.remove('dimmed');
        arc.classList.add('dimmed');
      } else if (mode === 'arc') {
        sector.classList.add('dimmed');
        radii.classList.add('dimmed');
        arc.classList.remove('dimmed');
      }
    }
  </script>
</body>
</html>

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta name="aspect-ratio" content="4:3">
  <style>
    * { box-sizing: border-box; margin: 0; padding: 0; }
    body {
      font-family: system-ui, -apple-system, sans-serif;
      color: #1e2945;
      background: #ffffff;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: space-between;
      min-height: 100%;
      padding: 12px;
      user-select: none;
    }
    .toolbar {
      display: flex;
      gap: 8px;
      width: 100%;
      max-width: 380px;
      justify-content: center;
      margin-bottom: 4px;
    }
    .btn {
      flex: 1;
      padding: 8px 10px;
      font-size: 13px;
      font-weight: 600;
      color: #1e2945;
      background: #f1f5f9;
      border: 1px solid #cbd5e1;
      border-radius: 8px;
      cursor: pointer;
      transition: background 0.2s, color 0.2s, border-color 0.2s;
      text-align: center;
    }
    .btn.active {
      background: #1e2945;
      color: #ffffff;
      border-color: #1e2945;
    }
    .svg-wrap {
      width: 100%;
      max-width: 380px;
      flex: 1;
      display: flex;
      align-items: center;
      justify-content: center;
    }
    svg {
      width: 100%;
      height: auto;
      display: block;
    }
    .formula-bar {
      font-size: 15px;
      font-weight: 700;
      color: #1e2945;
      background: #f8fafc;
      border: 1px solid #e2e8f0;
      border-radius: 20px;
      padding: 6px 16px;
      margin-top: 4px;
      display: flex;
      align-items: center;
      gap: 6px;
    }
    .c-orange { color: #ea580c; }
    .c-blue { color: #0284c7; }
    
    /* Transitions */
    line, circle, path, text, g {
      transition: opacity 0.3s ease, stroke-width 0.3s ease;
    }
  </style>
</head>
<body>

  <div class="toolbar">
    <button class="btn active" id="btn-all" onclick="setMode('all')">Compare</button>
    <button class="btn" id="btn-radius" onclick="setMode('radius')">Radius (<span class="c-orange">r</span>)</button>
    <button class="btn" id="btn-diameter" onclick="setMode('diameter')">Diameter (<span class="c-blue">d</span>)</button>
    <button class="btn" id="btn-relation" onclick="setMode('relation')">d = 2r</button>
  </div>

  <div class="svg-wrap">
    <svg viewBox="0 0 360 280">
      <defs>
        
        <pattern id="grid" width="20" height="20" patternUnits="userSpaceOnUse">
          <path d="M 20 0 L 0 0 0 20" fill="none" stroke="#f1f5f9" stroke-width="1"/>
        </pattern>
        <marker id="arrow-o" viewBox="0 0 6 6" refX="3" refY="3" markerWidth="4" markerHeight="4" orient="auto">
          <path d="M 0 0 L 6 3 L 0 6 z" fill="#ea580c" />
        </marker>
        <marker id="arrow-b" viewBox="0 0 6 6" refX="3" refY="3" markerWidth="4" markerHeight="4" orient="auto">
          <path d="M 0 0 L 6 3 L 0 6 z" fill="#0284c7" />
        </marker>
      </defs>

      <rect width="360" height="280" fill="url(#grid)" rx="12" />

      
      <circle cx="180" cy="140" r="100" fill="#f8fafc" stroke="#94a3b8" stroke-width="2.5" stroke-dasharray="4 4" />

      
      <g id="grp-radius">
        <line x1="180" y1="140" x2="83.4" y2="114.1" stroke="#ea580c" stroke-width="3.5" stroke-linecap="round" />
        
        <circle cx="83.4" cy="114.1" r="4.5" fill="#ea580c" />
        <text x="68" y="112" font-size="13" font-weight="700" fill="#ea580c" text-anchor="end">A</text>
        
        <rect x="88" y="90" width="80" height="20" rx="5" fill="#fff" fill-opacity="0.9" />
        <text x="128" y="104" font-size="12" font-weight="700" fill="#ea580c" text-anchor="middle">r = 5 cm</text>
      </g>

      
      <g id="grp-diameter">
        <line x1="93.4" y1="190" x2="266.6" y2="90" stroke="#0284c7" stroke-width="3.5" stroke-linecap="round" />
        
        <circle cx="93.4" cy="190" r="4.5" fill="#0284c7" />
        <text x="82" y="202" font-size="13" font-weight="700" fill="#0284c7" text-anchor="end">B</text>
        <circle cx="266.6" cy="90" r="4.5" fill="#0284c7" />
        <text x="278" y="88" font-size="13" font-weight="700" fill="#0284c7" text-anchor="start">C</text>
        
        <g id="lbl-diameter">
          <rect x="180" y="162" width="90" height="20" rx="5" fill="#fff" fill-opacity="0.9" />
          <text x="225" y="176" font-size="12" font-weight="700" fill="#0284c7" text-anchor="middle">d = 10 cm</text>
        </g>
      </g>

      
      <g id="grp-relation" opacity="0">
        
        <line x1="93.4" y1="190" x2="180" y2="140" stroke="#ea580c" stroke-width="4.5" stroke-linecap="round" />
        
        <line x1="180" y1="140" x2="266.6" y2="90" stroke="#f97316" stroke-width="4.5" stroke-dasharray="5 3" stroke-linecap="round" />
        
        <rect x="95" y="132" width="60" height="18" rx="4" fill="#fff" fill-opacity="0.95" />
        <text x="125" y="145" font-size="11" font-weight="700" fill="#ea580c" text-anchor="middle">r = 5 cm</text>
        <rect x="205" y="68" width="60" height="18" rx="4" fill="#fff" fill-opacity="0.95" />
        <text x="235" y="81" font-size="11" font-weight="700" fill="#ea580c" text-anchor="middle">r = 5 cm</text>
      </g>

      
      <circle cx="180" cy="140" r="5" fill="#1e2945" />
      <circle cx="180" cy="140" r="2" fill="#ffffff" />
      <text x="180" y="128" font-size="14" font-weight="800" fill="#1e2945" text-anchor="middle">O</text>
    </svg>
  </div>

  <div class="formula-bar" id="formula">
    <span class="c-blue">d</span> = 2 × <span class="c-orange">r</span> = 10 cm
  </div>

  <script>
    function setMode(mode) {
      document.querySelectorAll('.btn').forEach(b => b.classList.remove('active'));
      document.getElementById('btn-' + mode).classList.add('active');

      const grpRadius = document.getElementById('grp-radius');
      const grpDiameter = document.getElementById('grp-diameter');
      const grpRelation = document.getElementById('grp-relation');
      const lblDiameter = document.getElementById('lbl-diameter');
      const formula = document.getElementById('formula');

      if (mode === 'all') {
        grpRadius.style.opacity = '1';
        grpDiameter.style.opacity = '1';
        grpRelation.style.opacity = '0';
        lblDiameter.style.opacity = '1';
        formula.innerHTML = '<span class="c-orange">r = 5 cm</span> &nbsp;|&nbsp; <span class="c-blue">d = 10 cm</span>';
      } else if (mode === 'radius') {
        grpRadius.style.opacity = '1';
        grpDiameter.style.opacity = '0.15';
        grpRelation.style.opacity = '0';
        lblDiameter.style.opacity = '0';
        formula.innerHTML = 'Radius: <span class="c-orange">r = 5 cm</span> (Center to Rim)';
      } else if (mode === 'diameter') {
        grpRadius.style.opacity = '0.15';
        grpDiameter.style.opacity = '1';
        grpRelation.style.opacity = '0';
        lblDiameter.style.opacity = '1';
        formula.innerHTML = 'Diameter: <span class="c-blue">d = 10 cm</span> (Across Center)';
      } else if (mode === 'relation') {
        grpRadius.style.opacity = '0.2';
        grpDiameter.style.opacity = '0.2';
        grpRelation.style.opacity = '1';
        lblDiameter.style.opacity = '0';
        formula.innerHTML = '<span class="c-blue">d</span> = <span class="c-orange">5 cm</span> + <span class="c-orange">5 cm</span> = <span class="c-blue">10 cm</span>';
      }
    }

    setMode('all');
  </script>
</body>
</html>

OGM.6.GM.4

Aligned learning resources

Related diagrams