Archit's Challenge 6
Geometry
Level
4
Let be a 18 sided regular polygon inscribed in a circle. Find the number of ways of selecting three points such that when they are joined they form an isosceles triangle but not equilateral.
The answer is 126.
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1 solution
when we select a point on the polygon there are 7 cases in which the given polygon become isoscelses but not equilateral and 18 points can be selected so total cases=18*7=126