The GOLD point in the left panel is chosen at random inside the equilateral triangle. The red, blue and green segments are lines drawn from the GOLD point and perpendicular to each of the sides. Their lengths vary in size as you move the GOLD point from place to place inside the triangle. However, the sum of their lengths is constant. What is the sum equal to? Why? Can you prove it?
[You can change the size of the equilateral triangle by dragging the BLACK dots.]
Would a similar thing be true in a square? Why or why not?
What about other regular polygons with an odd number of sides? with an even number of sides?
Under what circumstances can the red, green and blue lengths can form a triangle?
What is the probability that a point chosen at random inside the triangle will determine three lengths that can form a triangle?
Can you prove your conjecture?
[see further challenge below]

- GOING FURTHER
What positions of the GOLD dot determine an isosceles triangle?
Can you use the fact that the sum of the distances from any point in the interior of an equilateral triangle to its sides is constant to prove that -
knowing the area and the perimeter of a triangle does NOT uniquely determine the triangle