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### 5.4 Built-in Functions

Several built-in functions are provided: ‘sin’, ‘cos’, ‘tan’, ‘asin’, ‘acos’, ‘atan’, ‘sinh’, ‘cosh’, ‘tanh’, ‘asinh’, ‘acosh’, ‘atanh’, ‘exp’, ‘ln’, ‘log’, ‘abs’, ‘round’, ‘floor’, ‘ceil’, ‘factorial’, ‘Gamma’, ‘lnGamma’, ‘erf’, and ‘erfc’; the function ‘lnGamma’ is the natural logarithm of the ‘Gamma’ function.

The ‘sin’, ‘cos’, and ‘tan’ functions require either a dimensionless argument or an argument with dimensions of angle.

```You have: sin(30 degrees)
You want:
Definition: 0.5

You have: sin(pi/2)
You want:
Definition: 1

You have: sin(3 kg)
^
Unit not dimensionless
```

The other functions on the list require dimensionless arguments. The inverse trigonometric functions return arguments with dimensions of angle.

The ‘ln’ and ‘log’ functions give natural log and log base 10 respectively. To obtain logs for any integer base, enter the desired base immediately after ‘log’. For example, to get log base 2 you would write ‘log2’ and to get log base 47 you could write ‘log47’.

```You have: log2(32)
You want:
Definition: 5
You have: log3(32)
You want:
Definition: 3.1546488
You have: log4(32)
You want:
Definition: 2.5
You have: log32(32)
You want:
Definition: 1
You have: log(32)
You want:
Definition: 1.50515
You have: log10(32)
You want:
Definition: 1.50515
```

If you wish to take roots of units, you may use the ‘sqrt’ or ‘cuberoot’ functions. These functions require that the argument have the appropriate root. You can obtain higher roots by using fractional exponents:

```You have: sqrt(acre)
You want: feet
* 208.71074
/ 0.0047913202

You have: (400 W/m^2 / stefanboltzmann)^(1/4)
You have:
Definition: 289.80882 K

You have: cuberoot(hectare)
^
Unit not a root
```

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