## RC FunctionMath Engineering Class

```Public Function RC( _
ByVal vX As Variant _
, ByVal vY As Variant _
) As Variant```

### Calculate a double precision approximation to RC(X,Y) = Integral from zero to infinity of (1/2)(t+X)^(-1/2)(t+Y)^(-1) dt, where X is nonnegative and Y is positive.

Examples:
```    RC(1, 1) = 1
RC(1, 2) = 0.785398163397448
RC(2, 1) = 0.881373587019543
RC(2, 2) = 0.707106781186547```
```    RD Function
RF Function
RJ Function
DRC Function```
vX: Function returns Null if vX is Null or cannot be fixed up to a Double precision floating point number.
vY: Function returns Null if vY is Null or cannot be fixed up to a Double precision floating point number.

The routine calculates an approximation result to RC(X,Y) = integral from zero to infinity of

```              -1/2     -1
(1/2)(t+X)    (t+Y)  dt,```
where X is nonnegative and Y is positive. The duplication theorem is iterated until the variables are nearly equal, and the function is then expanded in Taylor series to fifth order. Logarithmic, inverse circular, and inverse hyperbolic functions can be expressed in terms of RC.