Problem 11 · 2012 Math Kangaroo
Medium
Geometry & Measurement
symmetry
How big is the angle α in the regular five-sided star shown?
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Answer: C — 36°
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Hint 1 of 2
Each point of a regular five-pointed star is an identical isosceles triangle.
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Hint 2 of 2
The tip angle of a regular pentagram star point is a familiar value.
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Approach: use the fixed tip angle of a regular pentagram
- The five points of a regular star are congruent by symmetry.
- Each point tip of a regular pentagram measures 36°.
- So α = 36°.
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