---
title: "ACOS (Transact-SQL) | Microsoft Docs"
ms.custom: ""
ms.date: "07/24/2017"
ms.prod: sql
ms.prod_service: "database-engine, sql-database, sql-data-warehouse, pdw"
ms.reviewer: ""
ms.technology: t-sql
ms.topic: "language-reference"
f1_keywords: 
  - "ACOS"
  - "ACOS_TSQL"
dev_langs: 
  - "TSQL"
helpviewer_keywords: 
  - "cosine"
  - "ACOS function"
  - "arccosine"
ms.assetid: 4ec6b46e-9438-4f0f-8b96-461edd84280a
author: MashaMSFT
ms.author: mathoma
manager: craigg
monikerRange: ">=aps-pdw-2016||=azuresqldb-current||=azure-sqldw-latest||>=sql-server-2016||=sqlallproducts-allversions||>=sql-server-linux-2017||=azuresqldb-mi-current"
---
# ACOS (Transact-SQL)
[!INCLUDE[tsql-appliesto-ss2008-all-md](../../includes/tsql-appliesto-ss2008-all-md.md)]

A function that returns the angle, in radians, whose cosine is the specified float expression. This is also called arccosine.
  
![Topic link icon](../../database-engine/configure-windows/media/topic-link.gif "Topic link icon") [Transact-SQL Syntax Conventions](../../t-sql/language-elements/transact-sql-syntax-conventions-transact-sql.md)
  
## Syntax  
  
```sql
ACOS ( float_expression )  
```  
  
## Arguments  
*float_expression*  
An [expression](../../t-sql/language-elements/expressions-transact-sql.md) of either type **float** or of a type that can implicitly convert to float. Only a value ranging from -1.00 to 1.00 is valid. Values outside this range return NULL, and ASIN will report a domain error.
  
## Return Types  
**float**
  
## Examples  
This example returns the `ACOS` value of the specified number.
  
```sql
SET NOCOUNT OFF;  
DECLARE @cos float;  
SET @cos = -1.0;  
SELECT 'The ACOS of the number is: ' + CONVERT(varchar, ACOS(@cos));  
```  
  
[!INCLUDE[ssResult](../../includes/ssresult-md.md)]
  
```sql
---------------------------------   
The ACOS of the number is: 3.14159   
  
(1 row(s) affected)  
```  
  
## See also
[Mathematical Functions (Transact-SQL)](../../t-sql/functions/mathematical-functions-transact-sql.md)  
[Functions](../../t-sql/functions/functions.md)