title: Calculating an angle relative to a reference line
body: <p><a href="https://i.stack.imgur.com/IjNYT.jpg" rel="nofollow noreferrer">PLEASE SEE PICTURE -angle relative to baseline</a>we've been struggling with this for a while. Assuming we have distance between our measurement point P0 and P3-P4 and as also between P0 and our reference line P1-p2. Can we calculate the angle of p3-p4 relative to p1-p2? Once we figure this out, we'll see our to program it for IOS. Thanks for anyone who can point me in the right direction. [PLEASE SEE PICTURE relative angle measurement][2]</p>