Using Math2 Class MethodsLet's write a program named UserMathDemo.java that makes use of some of the methods defined in the Math2 class. A typical use of the common logarithm function is to compute the pH of a liquid. The pH is defined as the negative of the natural logarithm of the concentration of hydrogen ion in the liquid. Equation 17.10
The hydrogen ion concentration in Eq. (17.10) is in units of moles per liter. The UserMathDemo class defines the getPH() method that returns the pH value based on a specified hydrogen ion concentration. The getPH() method makes use of the log10() method defined in the Math2 class. A catenary is the curve a uniform flexible cable will assume when supported at its ends and acted upon by a uniform gravitational force. The shape of the curve follows that of the hyperbolic cosine function shown in Eq. (17.11). Equation 17.11
The x -direction is parallel to the ground and the y -direction is perpendicular to the ground. The point (0, a ), where a is a positive number, is the lowest point of the curve. The UserMathDemo class defines the getCatenaryY() method that returns the value of y for a catenary curve based on specified values of x and a . It makes use of the cosh() method from the Math2 class. The source code for the UserMathDemo class is shown here. import TechJava.MathLib.Math2; public class UserMathDemo { // This method returns the pH of a liquid. // It tests for zero or negative numbers. public static double getPH(double concH) { concH = Math.max(concH,1.0e-30); return -Math2.log10(concH); } // This method returns the y-location of a flexible // cable public static double getCatenaryY(double x,double a) { return a*Math2.cosh(x/a); } public static void main(String args[]) { System.out.println("pH = "+getPH(3.4e-6)); System.out.println("catenary y = " + getCatenaryY(3.4,2.0)); } } Output ” pH = 5.46852108295 catenary y = 5.6566309157 |