How to find the perimeter?

Surely, each of us taught in school such an importantcomponent of geometry, as a perimeter. Finding a perimeter is simply necessary to solve a multitude of tasks. Our article will tell how to find the perimeter.

It is worth remembering that the perimeter of any figure is almost always the sum of its sides. Let's look at several different geometric shapes.

  1. A rectangle is a quadrilateral whose parallel sides are equal in pairs to each other. If one side is X and the other is Y, then we get the following formula for finding the perimeter of this figure:

    P = 2 (X + Y) = X + Y + X + Y = 2X + 2Y.

    An example of solving a problem:

    Suppose that the side X = 5 cm, the side Y = 10 cm. So, substituting these values ​​in our formula, we get - P = 2 * 5 cm + 2 * 10cm = 30 cm.

  2. A trapezoid is a quadrangle whose two opposite sides are parallel, but not equal to each other. The perimeter of the trapezoid is the sum of all four of its sides:

    P = X + Y + Z + W, where X, Y, Z, W are the sides of the figure.

    An example of solving a problem:

    Suppose that the side X = 5 cm, the side Y = 10 cm, the side Z = 8 cm, the side W = 20 cm. So, substituting these values ​​in our formula, we get - P = 5 cm + 10 cm + 8 cm + 20 cm = 43 cm.

  3. The perimeter of the circle (circumference) can be calculated from the formula:

    P = 2rπ = dπ, where r is the radius of the circle, d is the diameter of the circle.

    An example of solving a problem:

    Assume that the radius r of our circle is 5 cm,then the diameter d will be equal to 2 * 5 cm = 10 cm. It is known that π = 3,14. So, substituting these values ​​in our formula, we get - P = 2 * 5 cm * 3.14 = 31.4 cm.

  4. If you need to find the perimeter of a triangle,then you may encounter a number of problems with this, since triangles can have very different shapes. For example, there is a sharp, obtuse, isosceles, rectangular or equilateral triangle. Although the formula for all kinds of triangles is:

    P = X + Y + Z, where X, Y, Z are the sides of the figure.

    The problem is that when solving many problems at theFinding the perimeter of this figure You will not always know the lengths of all sides. For example, instead of information about the length of one of the sides, you can have a degree of angle or the length of the height of a particular triangle. This will significantly complicate the task, but it will not make its solution unrealistic. On how to find the perimeter of a triangle, what form it could not be read "How to find the perimeter of a triangle?".

  5. The perimeter of a figure such as a rhombus is also found asand the perimeter of the square, because the rhombus is a parallelogram that has equal sides. Find out how to find the perimeter of a square by reading the article on our website "How to find the perimeter of a square?".

    Now you know how to find the side of the perimeter of the geometric figure that you need!

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