So I have some variables $\,x_{1},\, x_{2},\, \nu\, =\, 12.654,\, 13.487,\, 0\,$ and the following function:
$\dfrac{(x_{1}\cdot(-BesselK(\nu,x_{1}\cdot125))\cdot BesselI(\nu,x_{2}\cdot125))-(x_{2}\cdot BesselK(\nu+1,x_{1}\cdot 125)\cdot BesselI(\nu+1,x_{2}\cdot 125))}{\dfrac{-1}{125\cdot x_{1}}}$
What's my problem? Well even though the final output is a reasonable number, the output of the Bessel functions are either super-huge or super-small and the calculation requires quad-precision (which is very sluggish). I need to scale down the value going into the Bessel function but I need to be able to get the end result to be the same as if I used quad-precision.
Thank you.