You will need
  • - Notebook;
  • - the range;
  • pencil;
  • - handle;
  • calculator.
Instruction
1
A Pentagon is a polygon with five angles. The pentagons are right and wrong. Regular Pentagon is a convex polygon in which all sides and all angles are equal.

Irregular Pentagon is a polygon with sides and angles which are not equal. In the basic course of geometry often deals with the correct pentagons.
2
The perimeter of a polygon is the sum of the lengths of all its sides. To find the perimeter of a Pentagon calculate the length of each side, and then fold them.
3
If the task is given that the side of a regular Pentagon АВСDF equal to 5 cm, then its perimeter will be equal to:

P = 5АВ

P = 5*5 = 25

In this case, you just multiply the length of a side of a Pentagon the number of sides, because they are all equal to each other (Fig.1).
4
If the task was found irregular Pentagon, you must first find the length of each side, and then fold them.
5
For example, in the problem says that IN = 8, CO = 4, BC = 7, angle BOA = 90, the angle OAM = 45, Ω = 3, AB = DF, BC = CD. First consider the triangle AOB: IN = 8. From the condition it follows that AO = CO = 4. Triangle AOB is a right triangle. AO and CO are the legs, AB is the hypotenuse. By the Pythagorean theorem, the square of the hypotenuse is equal to the sum of the squares of the other two sides.
6
Therefore AB ^2 = AO ^2 + CO ^2.

AV ^2 = 8^2 + 4^2

AB ^2 = 64 + 16

AB ^2 = 80

AB = √80

AB = of 8.94

AB = DF = OF 8.94.
7
Then consider the triangle АОF. AO = CO = 4, Ω = 3. Angle AOB = DОF = 90 (as lying crosswise). Therefore, AOM = ВОD (like lying crosswise), and therefore AOM + ВОD = 360 - AOW + DОF = 180. AOM = 90.

It follows that the triangle АОF – rectangular.

So angle AMO = AOM – OAM,

AMO = 90 – 45, AMO = 45.
8
Consequently, the АОF triangle is isosceles. In an isosceles triangle opposite the equal angles are equal sides. Then AM = OM = 3.

Hence AF = 2AM = 6.
9
Now you can calculate the perimeter of a Pentagon АВСDF.

R = 8,94*2+7*2+6

P = 37,88