I want to find the blue point
I know the red point b
and the angle between 2 radii

image

CodePudding user response：

We know that the red point has coordinates (B.x, B.y). We know the origin point (A.x, A.y). We know the angle between the points theta. We want to find (C.x, C.y). I will be assuming 2d geometry, as this is what your reference shows.

Using a rotation matrix, we can subtract B by A to place A at the origin, then applying the matrix with the angle given.

Thus, given

B_new = (B.x - A.x, B.y - A.y),

C = (B_new.x * cos(theta) - B_new.y * sin(theta), B_new.x * sin(theta) B_new.y * cos(theta)) (A.x, A.y)