Root Function In Java Applet

I like to know how to write root function in java applet. I know it in java function. Ex:

import java.lang.*;
public class Maths {
public static void main(String[] args) {
// get two double numbers numbers
double x = 9;
double y = 25;
// print the square root of these doubles
System.out.println("Math.sqrt(" + x + ")=" + Math.sqrt(x));
System.out.println("Math.sqrt(" + y + ")=" + Math.sqrt(y));
}
}

working fine. but If I tried in applet it's not working. Ex:

evap_trans = 0.0135 * SRAD * ( TMEAN + 17.78) * Math.sqrt(TMAX - TMIN);

If I execute above said formulae with out "Math.sqrt" results are ok. If I used then results shows ZERO.