A regular pentagon - Math Central

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Question from Jamie, a student:

A regular pentagon is inscribed in a circle of radius 4.5 cm.
Determine its perimeter and area to one decimal place!

Thank YOU ! :)

Hi Jamie,

pentagon

The measure of angle BCA is 360/5 = 72^o. D is the midpoint of AB so angle ADC is a right angle. What is the measure of angle DCA? A little trigonometry tells you the rest.

Penny

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