+1493 The number of diagonals in a certain regular polygon is equal to $2$ times the number of sides. How many sides does this polygon have?
+1946 Let's say there are x sides on the polygon.
The number of diagonals can be represented by x∗(x−1)/2−x, meaning we can write the equation
2x=x∗(x−1)/2−x.
Solving for this equation, we find that x = 7, which is a heptagon.
A heptagon has 7 sides and indeed has 14 diagonals!
Thanks! :)
