Question 698752
Solution :
Let ABCD is an rectangle , 
we know that all angles of an rectangle is an right angle, 
Hence, the diagonal divides the rectangle in two right angled triangle. 
Let take one right angled triangle, ABC
in which Angle B = 90 degree, 
and diagonal AC = 13cm and AB = 10 cm 
hence by using pythagorus theorem , we get :
Ac^2 = AB^2 + BC^2 
13^2 = 10^2 + BC^2 
BC^2  = 13^2 - 10^2 
BC^2 = ( 13 - 10 ) ( 13 + 10)
BC^2 = 3 * 23 
BC = sqrt ( 69) 

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