00:01
In order to find the perimeter of this pentagon, we're first going to find what is the length of side a .e and multiply times five because a pentagon has five equal sides.
00:10
But in order to find this length, we need more information than what is given.
00:15
Let's just start finding this angle form at the red position.
00:21
If we'll draw all the angles on the center of the pentagon, we form a circle.
00:27
A circle has 360 degrees.
00:31
We have five of those angles.
00:35
360 divided by five is equal to 72 degrees.
00:41
So this angle is equal to 72 degrees.
00:46
From the definition of a pentagon, all the internal angles of a pentagon are equal to 108 degrees.
00:53
That means the angle form here at e is equal to 100 degrees.
00:57
108 degrees.
01:00
These two angles are going to be just half of 108 because the line ef is cutting the angle in half.
01:07
So 108 degrees divided by 2 is equal to 54 degrees.
01:16
This angle is equal to 54 degrees.
01:21
Let's rebuild triangle a fe on this position.
01:26
A.
01:28
E.
01:29
Here is a, here is f, here is e.
01:34
This side is 4 inches.
01:37
This angle is 72 and this angle is 54...