Java Reference

In-Depth Information

> Math.acos(0.5);

<< 1.0471975511965976

The
Math.atan()
returns the arctangent of a number. The result is an angle:

> Math.atan(Math.sqrt(3)); // Same as Math.PI/3

<< 1.0471975511965976

Warning: Rounding Errors

You might have noticed that some of the values in the previous examples

were not exactly accurate. For example, sin(π/6) should be 0.5, yet

Math.sin(Math.PI/6)
returns 0.49999999999999994.

This is to be expected when dealing with floating-point decimal numbers.

Computers have lots of trouble dealing with decimal fractions (as they work

in binary) and the answers can vary from one platform to another.

Another problem is that the value of π using
Math.PI
is only given correct

to 16 significant figures, which will affect the overall accuracy.

These rounding errors are no big deal for most web applications. Whenever

you perform any calculations, make sure that your program doesn't rely on

exact answers, and has some degree of tolerance instead.

Random Numbers

The
Math.random()
method is used to create random numbers, which can be very use-

ful when writing programs. Calling the method will generate a number between 0 and 1,

like so:

> Math.random();

<< 0.7881970851344265

To generate a random number between 0 and another number, we can multiply the value

by that number. The following code generates a random number between 0 and 6: