# CODESYS ATAN

Instructions · `ATAN` · verification: source checked

ATAN is an IEC operator in the CODESYS Development System that returns the arctangent of a number. The result is computed in radians. It can be written in ST (for example q := ATAN(0.5);) or placed as a block in FBD.

## Specification

| Property | Value |
|---|---|
| Language | iec 61131 3 |
| Code | ATAN |
| Syntax | q := ATAN(0.5); |
| Dialect | CODESYS |

## Study notes

- The result is computed in radians, not degrees.
- Input variables that measure the angle in radians may be any numeric basic data type.
- Output variables are permitted to be REAL or LREAL only.
- Worked example: ATAN(0.5) gives the result 0.463648.

## Sources

1. [Beckhoff Information System](https://infosys.beckhoff.com/content/1033/tc3_plc_intro/2529154955.html) (accessed 2026-10-26)
2. [CODESYS Group](https://content.helpme-codesys.com/en/CODESYS%20Development%20System/_cds_operator_atan.html) (accessed 2026-10-26)

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