# Futurebasic/Language/Reference/acos

## Acos edit

### Function edit

✔ Appearance ✔ Standard ✔ Console

### Syntax edit

radianAngle# = ACOS (expr)

### Description edit

Returns the arccosine of

in radians. In other words, if *expr*

represents the cosine of some angle, then *expr*`ACOS(`

returns the angle. The returned angle will be in the range of 0 to π radians (which corresponds to 0 to 180 degrees). *expr*)`ACOS`

always returns a double-precision result.

### Notes edit

No special notes.