To find the arccosine, or inverse cosine, of a number in VBA, we can use the Excel worksheet function **Acos()**.

`WorksheetFunction.Acos(x)`

In VBA, we can easily use trigonometric functions from the collection of VBA math functions. These VBA math functions allow us to perform trigonometry easily.

Unfortunately, there is not a function in VBA to calculate the arccosine of a number.

To find the arccosine of a number, we use the Excel worksheet function **acos()**.

Below is the VBA syntax to find the inverse cosine of a number.

`WorksheetFunction.Acos(x)`

The input to the **Acos()** function must be a double between -1 and 1. The return value will be a double between 0 and pi radians.

```
Debug.Print WorksheetFunction.Acos(0.5)
Debug.Print WorksheetFunction.Acos(0)
Debug.Print WorksheetFunction.Acos(-0.75)
'Output
1.0471975511965979
1.5707963267948966
2.4188584057763776
```

## Finding the Inverse Cosine of a Number in VBA

Arccosine is defined as the inverse of the cosine of a number.

Below, we show that if we pass a number to **Cos()** and then call the Excel **Acos()** worksheet function, we get back the same number.

```
Debug.Print WorksheetFunction.Acos(Cos(WorksheetFunction.Pi/3))
Debug.Print WorksheetFunction.Pi/3
'Output:
1.0471975511965976
1.0471975511965976
```

Hopefully this article has been beneficial for you to understand how to use the Excel **Acos()** worksheet function in VBA to find the arccosine of a number.

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