Numbers - Java - page 198

Solution

Use the trig functions in java.lang.Math . Like java.lang.Math.random() , all the meth-
ods of the Math class are static, so no Math instance is necessary. This makes sense because
none of these computations maintains any state. Note that the arguments for trigonometric
functions are in radians, not in degrees. Here is a program that computes one trigonometric
value and displays the values of e and PI that are available in the math library:

// Trig.java
System . out . println ( "The cosine of 1.1418 is " + Math . cos ( 1.1418 ));
System . out . println ( "Java's PI is " + Math . PI );
System . out . println ( "Java's e is " + Math . E );

The java.lang.StrictMath class is intended to perform the same operations as
java.lang.Math but with greater cross-platform repeatability.

Taking Logarithms

Problem

You need to take the logarithm of a number.

Solution

For logarithms to base e , use java.lang.Math 's log() function:

// Logarithm.java
double double someValue ;

// compute someValue...
double

double log_e = Math . log ( someValue );

For logarithms to other bases, use the identity that: