A polygon has eight sides. How many diagonals does it have?

To find the number of diagonals in a polygon, we use the formula n(n-3)/2 where n is the number of sides.

Step 1: Substitute the number of sides into the formula. In this case, n = 8. So, the formula becomes 8(8-3)/2.

Step 2: Simplify the expression in the parentheses. 8-3 = 5. So, the formula becomes 8(5)/2.

Step 3: Multiply 8 by 5 to get 40. So, the formula becomes 40/2.

Step 4: Divide 40 by 2 to get the number of diagonals. 40 divided by 2 equals 20.

So, a polygon with eight sides has 20 diagonals.