~~NOTOC~~
<=[[4rpl:start| Index]] \\
<= [[4rpl:start#Math]]  

====== acos ======
acos(-1) ->PiValue

===== Description =====
Calculates the arccosine of the input, returns the result in radians.

===== Examples =====
<code 4rpl>
trace(acos(-1)) #prints PI
</code>
<=[[4rpl:start| Index]]