The total interior angles of a pentagon = 540°

Each time we add a side (triangle to square, square to pentagon, pentagon to hexagon) we add another 180°.

Triangle to pentagon

Triangle		Square		Pentagon
`180°`	`+`	`180°`	`+`	`180°`	`=`	`540°`

The total internal angle of a pentagon = 540°

The total interior angles of a pentagon is 540 degrees

Now divide the total internal angle by the number of corners.

i.e. divide 540° by 5.

`540^circ/5=108^circ`

1		2		3		4		5
`108°`	`+`	`108°`	`+`	`108°`	`+`	`108°`	`+`	`108°`	`=`	`540°`