HomeMySQL Page 2 - Optimizing Queries with Operators, Branching and Functions, continued
Trigonometric Functions - MySQL
This article will give you a good grounding in operators, branching and functions in MySQL, so you can make the database, instead of your own code, do the bulk of the work. It is the second of three parts, and excerpted from chapter four of Beginning MySQL Database Design and Optimization: From Novice to Professional, written by Jon Stephens and Chad Russell (Apress; ISBN: 1590593324).
The trigonometric functions are useful for calculating lengths, arcs, and angles, as well as plotting curves and performing complex calculations involving waves.
NOTEWe wonít attempt to provide definitions or to explain trigonometry here. If you donít already know what they are or how to use them, check out the MathWorld web site, starting from http://mathworld.wolfram.com/Trigonometry. html.
MySQL provides the following trigonometric functions, where X is an angle expressed in radians:
SIN(X): Sine of X
COS(X): Cosine of X
TAN(X): Tangent of X
COT(X): Cotangent of X
NOTE The secant and cosecant trigonometric functions (often written as sec and csc in mathematical notation) can be obtained in MySQL by using the expressions 1 / COS(X) and 1 / SIN(X) , respectively.
The radian is a unit of angular measure defined such that 180 degrees is equal to p (pi) radians. (The number p is represented in MySQL as PI().) To convert radians to degrees, you can use the DEGREES() function, and to convert from degrees to radians, use the RADIANS() function.
The inverse trigonometric functions all return angle values expressed in radians:
ASIN(X): Arcsine of X
ACOS(X): Arccosine of X
ATAN(X): Arctangent of X
ATAN(X, Y) or ATAN2(X, Y): Arctangent of Y / X
NOTEMySQL stores p and e as double-precision floating-point values. This should be of sufficient accuracy for 99% of all applications requiring the use of these values.