Find the side and perimeter of a square whose diagonal is 10 cm.

In a square of side say a cm, any diagonal divide the square into two right triangles of equal dimensions.


Thus a2 + a2 = 102                                    


⇒ 2a2 = 100


⇒ a2 = 50


a = 5 cm


perimeter = 4a


= 4×5


= 20


Perimeter of square = 20cm

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