// CSE 142, Spring 2010, Marty Stepp
// This program demonstrates calling some methods from the Math class.
// Math methods use return values rather than directly printing their results.
// This program also demonstrates writing our own methods that return values,
// to perform computations such as line slope and object displacement.

public class MathFun {
    public static void main(String[] args) {
        double x = Math.pow(3, 4);
        System.out.println("The answer is " + x);
        
        // 3^4 + 9^2 + 14 * 2
        double y = x + Math.pow(9, 2) + 14 * 2;
        System.out.println("The second answer is " + y);
        
        Math.round(8.6);   // prints nothing
        
        // test the slope method by calling it, printing result
        double s = slope(1, 3, 5, 11);
        System.out.println(s);
        
        // test the displacement method
        double d = displacement(3.0, 4.0, 5.0);
        System.out.println("The displacement is " + d);
        
        double d2 = displacement(7.2, 1.0, 30.0);
        System.out.println("The second displacement is " + d2);
    }
    
    // Returns the slope of the line between the given points.
    // Assumes that x1 does not equal x2.
    public static double slope(int x1, int y1, int x2, int y2) {
        double dy = y2 - y1;
        double dx = x2 - x1;
        double result = dy / dx;
        return result;
    }
    
    // Computes and returns the change in position (displacement) of a moving
    // body with the given initial velocity v0 in m/s, the given 
    // acceleration a in m/s^2, over the given interval of time t in s.
    public static double displacement(double v0, double a, double t) {
        // v0t + (1/2)at^2
        double answer = (v0 * t) + 0.5 * a * Math.pow(t, 2);
        return answer;
    }
}