Bo cheo goc the div dung HTML va css

by Hoang_Van_Trinh

HTML

<!DOCTYPE html>
<html>
<head>

</head>
<body>
<div class="rectangle"></div>
<div class="triangle-tl " ></div>
<div class="trapezoid-tl"></div>
</body>
</html>

CSS

.rectangle {
   position: absolute;
	width: 200px;
   height: 150px;
   border: 5px solid red;  
}

.trapezoid-tl {
  border-bottom: 5px solid red;
  border-left: 5px solid transparent;
  border-right: 5px solid transparent;
  top: 24px;
  left: -1px;
  height: 0;
  width: 45px;
  position: absolute;
  z-index: 3;
  transform: rotate(-45deg);
}
.triangle-tl {
  position: absolute;
  z-index: 2;
  width: 0;
  height: 0;
  background: white;
  border-bottom: 33px solid white;
  border-left:  33px solid transparent;
}