Perimeter (P) – the sum of lengths of all parties of a figure, and at a quadrangle their four. Means to find quadrangle perimeter, it is necessary just to put lengths of all its parties. But such figures as a rectangle, a square, a rhombus, that is the correct quadrangles are known. Their perimeters are defined by special ways.
Instruction
1. If this figure - a rectangle (or a parallelogram) AVSD, then it has the following properties: the parallel parties are in pairs equal (see the drawing). AV = SD and EXPERT = VD. Knowing such relation of the parties in this figure, it is possible to remove rectangle perimeter (and a parallelogram): Р = AV + SD + EXPERT + VD. Let some parties will be equal to number and, others – to number in, then P = and + and + in + in = 2*a = 2 * in = 2 * (and + c). Example 1. AV = are equal to SD in AVSD rectangle of the party = 7 cm and the EXPERT = to VD = 3 cm. To find perimeter of such rectangle. Decision: Р = 2 * (and + c). Р = 2 * (7 +3) = 20 cm.
2. Solving problems for the sum of lengths of the parties with the figure called a square or a rhombus it is necessary to apply a little modified formula of perimeter. A square and a rhombus – the figures having the identical four parties. Proceeding from determination of perimeter, P = AV + SD + AC + of VD and allowing designation of length a letter and, P = and + and + and + and = 4*a. Example 2. The rhombus has length of the party of 2 cm. To find its perimeter. Decision: 4*2 cm = 8 cm.
3. If this quadrangle is a trapeze, then in this case it is just necessary to put lengths of four of its parties. Р = AV + SD + EXPERT + VD. Example 3. To find AVSD trapeze perimeter if its parties are equal: AV = 1 cm, SD = 3 cm, EXPERT = 4 cm, VD = 2 cm. Decision: Р = AV + SD + EXPERT + VD = 1 cm + 3 cm + 4 cm + 2 cm = 10 cm. There can be it that the trapeze will be ravnoboky (at it two sides are equal), then its perimeter can come down to a formula: Р = AV + SD + the EXPERT + VD = and + in + and + with = 2*a + in + page. Example 4. To find perimeter of a ravnoboky trapeze if its side sides are equal to 4 cm, and the bases - 2 cm and 6 cm. Decision: Р = 2*a + in + with = 2 * 4 cm + 2 cm + 6 cm = 16 cm.