I have been studying about ECDSA in right here.
Step 11 says that
you solely want the ‘x‘ worth (20 bytes) for the signature, and that worth might be known as ‘R‘
Does that say that R is the x-coordinate of the general public key.
However I do not see that occuring in a uncooked transactions.
For the pizza transaction, it is scriptSig appears like that：
The primary one is signature,the second is the general public key.
I do not see any relationship between the 2 gadgets.