00:01
In this question, we're given this shape that is formed by five similar triangles.
00:05
One, two, three, four, five.
00:14
Now, given that it forms a pentagon within the shape here in the pentagon, you can see that they have the same length in each side.
00:28
So, it's a regular pentagon.
00:30
Now, we want to find the angle alpha.
00:32
Far.
00:33
Now let's find one of the interior angles of the pentagon.
00:37
Since they are regular pentagon, all the angles are the same.
00:43
So in general, for a n -sided polygon or what we call an n -gun, the total interior angles is 180 degrees times n minus 2.
01:04
So in this case, the total interior angle for the pentagon where n is 5, the total interior angle is 180 degrees times 5 minus 2 and that will be 540 degrees.
01:25
So one interior angle of a pentagon is 540 degrees divided by 5, it will be 108.
01:39
So over here is 108 degrees...