Geometry problem (26) Question: calculate x in the picture below: 1.Trigonometric approach Solving this equation is rather difficult. Let's make a graph: so x is about 10 degrees, most likely exactly 10 degrees. 2.The geometric approach The 10 degree angle reminds of a regular 36 polygon. After some experimentation the following picture emerged: The 7x and 6x arcs are calculated with the Theorem of Thales. We see: 7x + 6x + 5x = 18x = 180 degrees. x = 10.