title: Work out co-prime of two numbers in java
body: <p>I have two BigIntegers holding prime numbers.</p>
  
  <pre><code>BigInteger a = BigInteger.probablePrime(16, new Random());
  BigInteger b = BigInteger.probablePrime(16, new Random());
  BigInteger c;
  </code></pre>
  
  <p>How would I find the co-prime of these two BigIntegers and store it in c;</p>