Computational geometry

• Fast 2D Line–Triangle Intersection Test
  Test whether an infinite 2D line intersects a triangle using three cross products, without calculating an intersection point or dividing.
• How to Approximate a Hypotenuse Without a Square Root
  Estimate a hypotenuse without a square root using the larger side plus one third of the smaller side, and see the method's error.
• How Does the Closest-Pair-of-Points Algorithm Work?
  The divide-and-conquer closest-pair algorithm finds the nearest two points in 2D in O(n log n) time by checking a narrow strip after each split.