Spot the error in the proof, Calculus?

x^2=x*x

x*x=x+x+x+x.....+x
x^2=x+x+x+x+x+x.....+x
Taking the derivative:

2x=1+1+1+1+1.....+1=x
2x=x
2=1

2 obviously doesn't equal 1, so why isn't this true? Everything seems true.

Demiurge422019-04-12T16:24:11Z

x^2=x+x+x+x+x+x.....+x

This equation is only true for integers. It doesn't even make sense for non-integers. An expression that is only defined for integers will not be differentiable anywhere.

llaffer2019-04-11T21:18:09Z

A description of what happened is explained here: https://jeremykun.com/2011/10/25/false-proof-1-2-with-calculus/