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Built in Functions » Histórico » Revisión 2

Revisión 1 (Federico Vera, 2018-06-09 23:54) → Revisión 2/10 (Federico Vera, 2018-06-09 23:55)

# Built in Functions 
 There are a number of built-in functions, that usually just map with the corresponding [`java.util.Math`](https://docs.oracle.com/javase/8/docs/api/java/lang/Math.html) methods (so all of the same restrictions apply), this functions are: 

 ## Trigonometric Functions: 
 * `sin(x)`: Sine of an angle expressed in radians 
 * `cos(x)`: Cosine of an angle expressed in radians 
 * `tan(x)`: Tangent of an angle expressed in radians 

 ## Inverse Trigonometric: 
 * `asin(x)`: Arc sine in the range [-π/2, π/2) 
 * `acos(x)`: Arc cosine in the range [0, π) 
 * `atan(x)`: Arc tangent in the range [-π/2, π/2)  

 ## Hyperbolic Functions: 
 * `sinh(x)`: Hyperbolic sine `(e^x - e^(-x)) / 2` 
 * `cosh(x)`: Hyperbolic cosine `(e^x + e^(-x)) / 2` 
 * `tanh(x)`: Hyperbolic tangent `(e^x - e^(-x)) / (e^x + e^(-x))` 

 ## Logarithms 
 * `log(x)`: Base 10 logarithm of `x`  
 * `log1p(x)`: Base 10 logarithm of `(x + 1)` 
 * `log10(x)`: Base 10 logarithm of `x` 
 * `log2(x)`: Base 2 logarithm of `x` 

 ## Misc 
 * `pow(b, e)`: `b` to the power of `e` 
 * `sqrt(x)`: Square root of `x` 
 * `cbrt(x)`: Cube root of `x` 
 * `exp(x)`: `e` to the power of `x` 
 * `expm1(x)`: `e` to the power of `x` minus 1 (`e^x - 1`) 
 * `signum(x)`<sup>1</sup>: Signum of `x` (`-1, 0, 1` for `< 0`, `= 0` and `> 0` respectively) 
 * `abs(x)`: Absolute value of `x` 
 * `ceil(x)`: First integer closest to negative infinity greater than or equal `x`  
 * `floor(x)`: First integer closest to positive infinity less than or equal `x`  

 ## Constants 
 * `pi()`: Ratio of the circumference of a circle to its diameter `3.14159265358979323846` 
 * `e()`: Base of the natural logarithm `2.7182818284590452354` 

 ## Disabling built-in functions 
 Since version `0.6-riddler` ([commit](https://gitlab.com/riddler_arg/exp4j/commit/28c731ea9a6140871a2ee2e0373cd13751d2e494)) you can disable all built-in functions like this: 

 ~~~Java 
     Expression e = new ExpressionBuilder("x + 3") 
                       .disableBuiltInFunctions() //<-- 
                       .variable("x") 
                       .build(); 
 ~~~ 

 Remember that since constants are also defined as functions this will also disable them. 

 ## Code 
 The code for the functions is [here](https://gitlab.com/riddler_arg/exp4j/blob/master/src/main/java/net/objecthunter/exp4j/function/Functions.java). 

 ## 
 <sup>1</sup> This is the only method not implemented using it's corresponding `java.util.Math` method.