CodePen

HTML

            
              <div class="triangle"></div>
<div class="uglyTriangle"></div>
            
          
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CSS

            
              div {
  width: 0;
  height: 0;
  margin: 10px;
}

.triangle {
  border-top: 20px solid #000;
  border-left: 20px dotted transparent;
  border-right: 20px dotted transparent;
}

.uglyTriangle {
  border-top: 20px solid #000;
  border-left: 20px solid transparent;
  border-right: 20px solid transparent;
}
            
          
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JS

            
              
            
          
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