1.

Prove that in a quadrilateral the sum of all the sides is greater than the sum of its diagonals.

Answer»

Given:

Let ABCD is a quadrilateral with AC and BD as its diagonals

To Prove:

Sum of all the sides of a quadrilateral is greater than the sum of its diagonals

Proof:

Consider a quadrilateral ABCD where AC and BD are the diagonals

AB+BC > AC (i) (Sum of two sides is greater than the third side)

AD+DC > AC (ii)

AB+AD > BD (iii)

DC+BC > BD (iv)

Adding (i), (ii), (iii), and (iv)

AB+BC+AD+DC+AB+AD+DC+BC > AC+AC+BD+BD

2(AB+BC+CD+DA) > 2(AC+BD)

AB+BC+CD+DA > AC+BC

Hence, proved that the

Sum of all the sides of a quadrilateral is greater than the sum of its diagonals



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