Determinate a normal versor for the surface $S$ in $\Bbb R^3$ with global parametrization $\varphi:\Bbb R^2\to\Bbb R^3$ given by $\varphi(u,v)=(e^u,u+v,u)$, and compute the angle betweem the coordinate curves.
Try: I understand that a versor is a unit vector, so to find the versor I have a formula which is, $$N=\dfrac{\varphi_u\times \varphi_v}{|\varphi_u\times\varphi_v|}$$
I find all that and I have my vector. But I don't know how to compute the angle between the coordinate curves, I don't have a formula for that, could someone help me.