Best Answer

to make any line you need two points..

so.. a pentagon has 5 vertices - ie. 5 points

so how many ways can you select a combination of 2 - out of 5 points..

1,2,3,4,5

- (1,2)
- (1,3 )
- (1,4 )
- (1,5 )
- (2, 3)
- (2,4 )
- (2,5 )
- (3, 4)
- (3, 5)
- (4, 5)

so, there you have it -> total of 10 ways :) -> so 10 diagonals.

now of course you could also think like this: ie. pose the question as follows

how many ways can one select r number of goods from P number of total items:

here in YOUR EXAMPLE: R =2 AND P =5

AND well, its a combination of r froma set of p -> which you are looking at:

hence the answer = n c r = factorial n divided by factorial r = 5! / [2! x 3!] =

= (5 X4X3X2X1) / (2x1).(3x2x1) = 5 x 2 = 10

Summarize now: you need a combination of 2 from a total of 5 .. and the formula is => factorial 5 - divided by factorial 3 divided by factorial 2

or mathematically expressed as n C r -> again, in your example, n = 5 [ pentagon] r = 2 [ you are looking for diagonals and it takes two to tango]

[ note: 2,1 is the same as 1,2 and 2,3 is the same as 3,2 and 2,4 is the same as.... etc etc ....]

cheers

olga lednichenko

Q: How many diagnals in a pentagon shape?

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A pentagon itself is one shape. It has five sides.

a pentagon has 5 sides, a regular pentagon has 5 EQUAL sides A Regular Pentagon is a shape that has equal angles and side lengths. It is type of Pentagon. Pentagons do not have to have equal sides and lengths.

Fort Sumter was a pentagon.

I would say a convex irregular pentagon. Convex as any line drawn between two points can be contained inside the shape, Pentagon since it is 5 sided, but irregular because if you look at it topographically, it looks like the side of a house. As opposed to the true pentagon whose east-west walls are angled out and the sum of the angles is 540 degrees.

because bob named it that... Ok? If you mean the building, it is because it is pentagonal in shape. If you mean the shape, "pentagon" is greek for "five angles". Actually, I think the Pentagon is named so because of the five branches of the military: U.S. Army, Marine Corps, Navy, Air Force, Coast Guard. And then it was built to be five sided to represent those branches.

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A pentagon has five internal angles.

yes a pentagon is a rigid shape * * * * * I am afraid that it is not.

what is a diacnal

5 sides A pentagon is any five-sided shape.

A pentagon itself is one shape. It has five sides.

It has 2 diagonals

A shape with 5 sides is called a pentagon.

A five sided shape is called a pentagon.

pentagon

A Morning Glory, like many other flowers, have a pentagonal shape.

They are both the same. Pentagon is just a shorter way of saying the pentagon building. As for if you meant the shape pentagon, it is called the pentagon because it's shape is a pentagon.

This is a misguided question since a pentagon is NOT a rigid shape.