Optimizing Queries with Operators, Branching and Functions, continued - Trigonometric Functions (
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The trigonometric functions are useful for calculating lengths, arcs, and angles, as well as plotting curves and performing complex calculations involving waves.
NOTE We won’t attempt to provide definitions or to explain trigonometry here. If you don’t 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
NOTE MySQL 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.
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