# Thread: Diagonals in a regular pentagon

1. ## Diagonals in a regular pentagon

How many diagonals does a regular pentagon have?

2. ## 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?

3. ## Re: Diagonals in a regular pentagon

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.

4. ## Re: Diagonals in a regular pentagon

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?

5. ## Re: Diagonals in a regular pentagon

I got 4 diagonal lines. Is that the answer?
You missed one diagonal, redraw the figure and find out which one you missed.

6. ## 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.