Question

I have 2 points P1 and P2. I need to find the P3, in order that

• all points to be on the same line;
• P3 should be at the distance d from the P2 (away from P1)

I started a complicated system apparently hardly to resolve…

PS.

Vectorial answers is cool, but I use C# and don’t know how to add vectors over there.

Answer 1

P3 = P2 + d * ±(P2 - P1) / |P2 - P1|

EDIT:

Because shopping is easy:

mag = sqrt((P2x - P1x) ** 2 + (P2y - P1y) ** 2)
P3x = P2x + d * (P2x - P1x) / mag
P3y = P2y + d * (P2y - P1y) / mag