Question

what is the number of diagonal in in a polygon of 10 sides?​

Answer 1

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Pls refer to the attachment

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Answer 2

Decagon (10 sides): n(n-3)/2 = 10(10-3)/2 = 10*7/2 = 70/2 = 35 diagonals. Icosagon (20 sides): n(n-3)/2 = 20(20-3)/2 = 20*17/2 = 340/2 = 170 diagonals.