This will require the properties of the rectangle:
In a rectangle, opposite sides are equal; the diagonals are equal and the intersection point is halved.
AD = 10 cm (by condition), the opposite side of the BC is also 10 cm.
The triangle BОС includes two more sides – BO and CO, these are halves of the diagonals. One diagonal BD = 8 cm (by condition), which means that the second diagonal of the AC is also 8 cm, and their halves are 4 cm each.
In a triangle BОС: ВС = 10 cm, BО = 4 cm, СО = 4 cm.
It remains to find the perimeter, that is, the sum of the sides: P = 10 + 4 + 4 = 18 cm.
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