**Public Function ACos( _
ByVal vX As Variant _
) As Variant**

**"Inverse Cosine" or "Arccosine" **

Angle whose cosine is X.

Inverse of the Cosine function.

**Examples:** ACos(-0.5) = 2.0943951023932
ACos(0) = 1.5707963267949
ACos(0.5) = 1.0471975511966
ACos(1) = -3.5527136788005E-15
ACos(1.5) = "-3.5527136788005E-15|0.962423650119205"
ACos("2.3|-4.5") = "1.10609748442001|2.31904592228528"

**See also:** Cosine Function
ASin Function
ATan Function
ACsc Function
ACosH Function
Arccos Function

**vX:** Function returns the principal value of the angle whose cosine (expressed in radians) is vX. Function returns Null if vX is Null or cannot be fixed up to a real or complex number (as defined by the ComplexStringToReals function). Complex numbers are represented within strings as "R|I" where R is the real part and I is the imaginary part.

**Note:** Microsoft named this function Arccos within their Derived Math Function help topic. Copyright 1996-1999 Entisoft

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