How to determine the distance to one point from another in a 3D coordinate system? I wonder how I can calculate the distance between two coordinates in a $3D$ coordinate-system.
Like this. I've read about the distance formula:
$$d = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2}$$
(How) Can I use that it $3D$ coordinates, or is there any other method?
Thanks!

In three dimensions, the distance between two points (which are each triples of the form $(x, y, z))$ is given by $$d= \sqrt{(x_2-x_1)^2 + (y_2-y_1)^2 + (z_2-z_1)^2}$$
