AMM = Automated Market Makers.
Spot price means how much B will I get for a given A. A and B being the two tokens of an AMM.
If we do trade like this we get dy tokens doe providing dx tokens and the slope will be dy/dx.
Now, if I do a smaller trade like this:
Note the blue line. And doing an even smaller trade:
Note the orange line.
As you can see the smaller the dx the slope starts to look like the tangent of the curve.
According to the constant product formulla the follwing equation must always hold.
Now, lets derive:
Now, as dx goed to 0:
