Geometry/trigonometry-finding areas of regualr polygons

Greaterpathmagician · 2009-10-11 21:33:04

Please help me with this quesiton

Find the area of each inscribed regular polygon

Thank you so much for any help

Last edited by Greaterpathmagician (2009-10-11 21:45:59)

bobbym · 2009-10-11 21:59:54

Hi Greaterpathmagician;

For the pentagon:

n = number of sides
r = radius

For your last one is that 10 sided with each side = 2 cm ? I can't see it clearly enough.

Last edited by bobbym (2009-10-11 22:19:04)

Greaterpathmagician · 2009-10-11 22:26:50

here is a larger image of the decagon

Greaterpathmagician · 2009-10-11 22:28:43

Thanks for the help. Can the formula be used to find the area of the other polygons

bobbym · 2009-10-11 22:31:34

Hi Greaterpathmagician;

Yes, when you know the radius:

You can use the perimeter formula for the decagon:

P = 10 * 2 = 20

Now since you have r and n you can use this form for the area:

Last edited by bobbym (2009-10-11 22:40:50)

Greaterpathmagician · 2009-10-11 22:36:25

Thanks

bobbym · 2009-10-11 22:42:13

Hi;

Glad to help. I have added some bits to the last post.

Last edited by bobbym (2009-10-11 22:45:57)

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