Having 2 coordinates calculating the 90 degree angle formula of the next point

Question

I have 2 coordinates, what would be the 90 degree formula to the next point I am drawing?

Say

A = 50.88259382849774,6.003988087177277
B = 50.88269282423443,6.0036662220954895
x = ?

Is it possible to calculate if a coordinate is on the 90 degree angle point of AB?

Answer 1

If $A = (a_1, a_2)$ and if $B = (b_1, b_2)$ then a point $(x_1, x_2)$ is on the line perpendicular to $AB$ through $B$ (your "x.") if and only if $(b_1-a_1)(x_1-b_1) + (b_2 - a_2)(x_2 - b_2) = 0$. This follows from the geometric definition of the dot product.