# Diagonals in a regular pentagon

• Sep 23rd 2013, 09:47 PM
Diagonals in a regular pentagon
How many diagonals does a regular pentagon have?

• Sep 23rd 2013, 10:39 PM
votan
Re: Diagonals in a regular pentagon
A pentagon is a polygon that have five sides. a diagonal in a polygon is the line that joins any two vertices. The best you to get your answer is to sketch a pentagon and draw the diagonals. How many diagonal you will count?
• Sep 24th 2013, 02:45 AM
Plato
Re: Diagonals in a regular pentagon
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How many diagonals does a regular pentagon have? Please help me on this problem! I would appreciate steps on how to get the answer or hints!

A pentagon has five vertices no three of which are collinear.
So 5 choose 2 is the number of line segments the vertices determine.
There are five edges. The rest are diagonals.

This process will work for any polygon.
• Sep 24th 2013, 07:28 PM
Re: Diagonals in a regular pentagon
Quote:

Originally Posted by votan
A pentagon is a polygon that have five sides. a diagonal in a polygon is the line that joins any two vertices. The best you to get your answer is to sketch a pentagon and draw the diagonals. How many diagonal you will count?

I got 4 diagonal lines. Is that the answer?
• Sep 24th 2013, 09:00 PM
votan
Re: Diagonals in a regular pentagon
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I got 4 diagonal lines. Is that the answer?

You missed one diagonal, redraw the figure and find out which one you missed.
• Sep 25th 2013, 08:02 PM
Re: Diagonals in a regular pentagon
I redrew the figure and I still got 4 diagonal lines. I tried 4 or 5 times and did it separately and compared my answers and I still got the same number of diagonal lines.
• Sep 25th 2013, 10:36 PM
votan
Re: Diagonals in a regular pentagon
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