---
name: "lapy3"
section: "3"
platform: "linux"
package: "lapack-doc"
version: "3.12.1-2"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/lapy3"
---

# lapy3(3)

lapy3: robust sqrt( x^2 + y^2 + z^2 )

## NAME

lapy3 - lapy3: robust sqrt( x^2 + y^2 + z^2 )

## SYNOPSIS

### Functions

double precision function **dlapy3** (x, y, z)\
 **DLAPY3** returns sqrt(x2+y2+z2).  real function **slapy3** (x, y, z)\
 **SLAPY3** returns sqrt(x2+y2+z2).

## Detailed Description

## Function Documentation

### double precision function dlapy3 (double precision x, double precision y, double precision z)

**DLAPY3** returns sqrt(x2+y2+z2).

**Purpose:**

```
!>
!> DLAPY3 returns sqrt(x**2+y**2+z**2), taking care not to cause
!> unnecessary overflow and unnecessary underflow.
!>
```

**Parameters**

*X*

```
!>          X is DOUBLE PRECISION
!>
```

*Y*

```
!>          Y is DOUBLE PRECISION
!>
```

*Z*

```
!>          Z is DOUBLE PRECISION
!>          X, Y and Z specify the values x, y and z.
!>
```

**Author**

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line **67** of file **dlapy3.f**.

### real function slapy3 (real x, real y, real z)

**SLAPY3** returns sqrt(x2+y2+z2).

**Purpose:**

```
!>
!> SLAPY3 returns sqrt(x**2+y**2+z**2), taking care not to cause
!> unnecessary overflow and unnecessary underflow.
!>
```

**Parameters**

*X*

```
!>          X is REAL
!>
```

*Y*

```
!>          Y is REAL
!>
```

*Z*

```
!>          Z is REAL
!>          X, Y and Z specify the values x, y and z.
!>
```

**Author**

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line **67** of file **slapy3.f**.

## Author

Generated automatically by Doxygen for LAPACK from the source code.