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<!DOCTYPE html>
<html>
<head>
<style> 
#example1 {
  border: 2px solid red;
  padding: 10px;
  border-radius: 2em / 5em;
}
#example2 {
  border: 2px solid red;
  padding: 10px;
  border-radius: 2em 1em 4em / 0.5em 3em;
}
</style>
</head>
<body>
<h2>border-radius: 2em / 5em:</h2>
<div id="example1">
  <p>Is equivalent to: border-top-left-radius: 2em 5em; border-top-right-radius: 2em 5em; border-bottom-right-radius: 2em 5em; border-bottom-left-radius: 2em 5em;</p>
</div>
<h2>border-radius: 2em 1em 4em / 0.5em 3em:</h2>
<div id="example2">
  <p>Is equivalent to: border-top-left-radius: 2em 0.5em; border-top-right-radius: 1em 3em; border-bottom-right-radius: 4em 0.5em; border-bottom-left-radius: 1em 3em;</p>
</div>
</body>
</html>