java - new error: Actual and formal argument lists differ in length -

trying finish assignment first year comp class. far everything's been okay, can't figure 1 error out. wondering if out here? tried changing variables doubles , didnt work.

import java.util.scanner;  public class cellphoneprogram {    public static scanner keyboard = new scanner(system.in);    //declare x , y coordinates each city    public static double xa = 100, xb = 100, xc = 340, xd = 230, ya = 360, yb = 360, yc = 250, yd = 140;      public static int getrange(int city) {      int range = 0;      system.out.println("what maximum distance (in km) center of city " + city + " may travel without losing service?");      range = keyboard.nextint();      return range;    }       /* error occurs here */    public static double distance(double xf, double xi, double yf, double yi) {      double distance = 0;      distance = math.sqrt((math.pow(xf - xi)) - (math.pow(yf - xi)));      return distance;    }      public static void main(string[] args) {      int city1, city2, city3, city4;      double distance1, distance2, distance3;        system.out.println("welcome cell phone service program, enter range of service 4 cities," +        " , calculate whether or not lose service.");      //get range function      city1 = getrange(1);      city2 = getrange(2);      city3 = getrange(3);      city4 = getrange(4);        system.out.println(city3);        //calculate distances cities      distance1 = distance(xb, xa, yb, ya);      distance2 = distance(xc, xb, yc, yb);      distance1 = distance(xd, xc, yd, yc);        system.out.println(distance1);    }  }

here's @ error:

file: c:\users\katie\documents\homework\cellphoneprogram.java  [line: 16]  error: method pow in class java.lang.math cannot applied given types;    required: double,double    found: double    reason: actual , formal argument lists differ in length  file: c:\users\katie\documents\homework\cellphoneprogram.java  [line: 16]  error: method pow in class java.lang.math cannot applied given types;    required: double,double    found: double    reason: actual , formal argument lists differ in length

this code still in progress, sorry messiness , incomplete code , that.

math.pow() requires 2 arguments not one. guessing want raise second power second argument should 2.

math.sqrt((math.pow(xf - xi,2)) - (math.pow(yf - xi,2))); 

see http://docs.oracle.com/javase/7/docs/api/java/lang/math.html#pow%28double,%20double%29