## Chi FunctionMath Reals Class

```Public Function Chi( _
ByVal vA As Variant _
, ByVal vX As Variant _
, ByVal vB As Variant _
) As Variant```

### "Hyperbolic Cosine Integral" Chi where A, X, and B are real numbers. Return 1 if A < X < B; .5 if X = A or X = B; 0 if X < A or X > B.

Summary:
```    A < X < B: Return 1
A = X or A = B: Return .5
X < A or X > B: Return 0```
Examples:
```    Chi(-5, 7, 10) = 1
Chi(-5, 10, 10) = .5
Chi(-5, 10, -20) = 0```
```    ChiVerify Subroutine
CosH Function```
vA: The lower bound of the range against which vX is tested. Function returns Null if vA is Null or cannot be fixed up to a number.

vX: The number which is tested to see if it is within, on the bounds of, or outside the range from vA to vB. Function returns Null if vX is Null or cannot be fixed up to a number.

vB: The upper bound of the range against which vX is tested. Function returns Null if vB is Null or cannot be fixed up to a number.

v1.5 Note: The behavior of this function is undefined when A > B.