math.acos

Return the arccos (inverse cosine) of num (in radians). This is equivalent to ${\displaystyle \arccos(x)}$. To convert the output to degrees, you can use math.deg (for example: math.deg(math.acos(0.5))).

Name	arccos
Lua function	math.acos
Usual notation	${\displaystyle y=\arccos(x)}$
Definition	${\displaystyle x=\cos(y)}$
Domain of x for real result	${\displaystyle -1\leq x\leq 1}$
Range of usual principal value (radians)	${\displaystyle 0\leq y\leq \pi }$

ExamplePrint the arccosine of user input
Read a line from the user, print its arccos in radians, then in degrees.
Code	<nowiki>local num = math.acos(tonumber(read())) print(num) print(math.deg(num)) </nowiki>
Output	Depends on what the user wrote. For instance, if they were to enter 0.5, the numbers printed would be 1.0471975512 (${\displaystyle {\frac {\pi }{3}}}$) and 60.

math.acos Function
Syntax math.acos( num : number )
Returns	number
API	math
Source	Lua (source)