1
$\begingroup$

In textbooks on differential geometry, the first fundamental form looks like $E^2+2FG+H^2$, and its length is calculated through the help of the dot product. However, the inner product did not exist. The analytic formula was known that $x_1x_2+y_1y_2+z_1z_2$ . Nor did the vector exist. So how did he prove it? Same story with the unit normal: in textbooks they use the cross product $r(u) \times r(v)$ But this did not exist either. Again, how did he manage to calculate it?

$\endgroup$
  • 2
    $\begingroup$ Try formatting it with MathJax $\endgroup$ – Euler_Salter Dec 26 '16 at 20:36
  • $\begingroup$ Who is "he" supposed to be? $\endgroup$ – Danu Dec 29 '16 at 23:31

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.