Formula Reversal

Hi everyone... I have an algorithm I can solve, however, cannot figure out how to derive variables from the answer.

It is based on the minimum curvature method.

L = Length
I = Inclination
A = Azimuth
Iup = Previous Inclination
Aup = Previous Azimuth

AngCh = Total Angle Change
Factor = Curve Factor

X = X position

Let L=6m, I=20 deg, A=35 deg, Iup=15 deg, Aup=45 deg

AngCH = ( DEGREES ( ACOS (( COS ( RADIANS( I-Iup ))) - ( SIN ( RADIANS ( Iup ))) *
( SIN ( RADIANS ( I ))) * ( 1-COS ( RADIANS ( A-Aup ))))))
= 5.817 deg

Factor = ( 2/RADIANS ( AngCH )) * TAN ( RADIANS ( AngCH ) / 2 = 1.001

X = ( L / 2 ) * (( SIN ( RADIANS ( I )) * SIN ( RADIANS ( A ))) +
( SIN ( RADIANS ( Iup )) * SIN ( RADIANS ( Aup )))) *
( IF ( AngCh=0,1,((( 2 / RADIANS ( AngCh )) * TAN ( RADIANS ( AngCh ) / 2 ))))) * Factor
= 1.140m

How do I derive the I and A variables, given I know the rest.

I=?
A=?
L=6
Iup=15
Aup=45


I've been trying to figure this out for months.

Thankyou all so much in advance ;)