Deducing an interior angle of a triangle-capture.png

Please refer the image.
How to figure out the angle α with only the following information
dClCr=RElmin+REinitr
The lines EinitCr and EinitD are perpendicular.
REinitr and Cr are unknown and will be deduced with the help of α.
Cl, RElmin, ψ, dClEinit are known.