1.

If a convex polygon has 170 diagonals. Find the number of sides of the polygon.

Answer»

Number of diagonals = nC2 – n = 170.

\(\frac{n(n - 1)}{2} - n = 170\)

n2 – n – 2n = 340 

⇒ x2 – 3x – 340 

(n + 17) = 0 

n = 20 or -17 

∵ n can’t be negative n = 20



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