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Friday, January 10, 2014

Regular Polygon Problems, 2

Category: Analytic Geometry, Plane Geometry

"Published in Newark, California, USA"

A regular hexagon of side 6 has its center at the origin and one diagonal along the x-axis. Find the coordinates of its vertices.

Solution:

A regular hexagon has 3 longest diagonals that passes thru the center. There are 9 diagonals of a regular hexagon in total. In this problem, let's consider a longest diagonal that lies along the x-axis. To illustrate the problem, it is better to draw the figure as follows

Photo by Math Principles in Everyday Life

There are 6 triangles inside the regular hexagon. Since all sides of a regular hexagon are equal, then it follows that the three longest diagonals are equal to each other and bisect each other at the center. If the two sides of each triangles are equal, then all triangles are isosceles triangles. Let's further analyze and label the figure as follows


Photo by Math Principles in Everyday Life

The vertex angle of each triangles can be calculated as follows
 
 

If the two sides of an isosceles triangle are congruent, then it follows that the base angles are congruent also. The base angle of an isosceles triangle is





Since all angles of a triangle are congruent, then all triangles in a regular hexagon are equiangular or equilateral. Let's consider one triangle in a regular hexagon in order to calculate the altitude or height, we have


Photo by Math Principles in Everyday Life

Apply Pythagorean Theorem in order to solve for the altitude or height, we have
 
 
 
 
 
 
   
Therefore, the coordinates of the vertices of a regular hexagon are