title: How to check if point is in line shadow
body: <p>I can't really figure out how exactly to phrase this question, so I made a crude graphic explaining what I'm trying to ask: <img src="https://i.stack.imgur.com/B2pwR.png" alt="enter image description here"></p>
  
  <p>Given a line comprised of two points, how would I go about checking if a given point was within the area relative to the line as displayed in the image? Sorry if there is a term for this that I didn't know.</p>