title: Unresolved reference sqrt() Kotlin
body: <p>I want to use :  (<a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.math/sqrt.html" rel="nofollow noreferrer">link</a>)</p>
  
  <pre><code>fun sqrt(x: Double): Double
  </code></pre>
  
  <p>which is a basic math function in my kotlin version :   </p>
  
  <blockquote>
    <p>kotlinc-jvm 1.2.0 (JRE 1.8.0_151-b12)</p>
  </blockquote>
  
  <p>Actually my code is :</p>
  
  <pre><code>fun main(args: Array&lt;String&gt;){ 
      println(doSqrt("16"));
  }
  
  fun doSqrt(num: String) : String{
      var number: Int = num.toInt();
      var nb: Double = number.toDouble();
      var result: Double = sqrt(nb);
      return (result.toString())
  }
  </code></pre>
  
  <p>but when I compile with </p>
  
  <blockquote>
    <p>kotlinc test.kt -include-runtime -d test.jar</p>
  </blockquote>
  
  <p>Result is :</p>
  
  <pre><code>test.kt:10:26: error: unresolved reference: sqrt
       var result: Double = sqrt(nb);
  </code></pre>
  
  <p>I try to import </p>
  
  <blockquote>
    <p>kotlin.Math</p>
  </blockquote>
  
  <p>It doesn't work I also try to import</p>
  
  <blockquote>
    <p>kotlin.*</p>
  </blockquote>
  
  <p>Same problem...</p>
  
  <p>Which way to use the sqrt function in Kotlin ?</p>