# Futurebasic/Language/Reference/asin

## Asin edit

### Function edit

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### Syntax edit

radianAngle# = asin( expr )

### Description edit

Returns the arcsine of

in radians. In other words, if *expr*

represents the sine of some angle, then *expr*`asin`

`(`

*expr*`)`

returns the angle. The returned angle will be in the range of -π/2 to +π/2 radians (which corresponds to -90 to +90 degrees). `asin`

always returns a double-precision result.

### Notes edit

No special notes.