The ACOS function returns the arccosine, or inverse cosine, of a number. The arccosine is the angle whose cosine is number. The returned angle is given in radians between 0 and π.

**Syntax**: =ACOS(number)

The ACOS function syntax has the following arguments:

**number:**A number between -1 and 1. It is the cosine of the angle that you wish to find.

**Example**: Let’s look at some Excel ACOS function examples and explore how to use the ACOS function as a worksheet function in Microsoft Excel:

**Syntax**: =ACOS(C2)

**Result**:

Based on the Excel spreadsheet above, the following ACOS examples would return:

**Syntax**: =ACOS(C3)

**Result**: 2.094395102

**Syntax**: =ACOS(C4)

**Result**: 2.278380764

**Syntax**: =ACOS(C5)

**Result**: 1.570796327

**Syntax**: =ACOS(C6)

**Result**: 0.86321189

**Syntax**: =ACOS(C7)

**Result**: 1.047197551

**Syntax**: =ACOS(C8)

**Result**: 0