If the length of a diagonal of a square is 18, find the perimeter of the square.

The length of a diagonal of a square is the side*sqrt(2). Let's call one side of the square: s

So we have 18 = s*sqrt(2)

18/sqrt(2) = s

18sqrt(2)/2 = s

9sqrt(2) = s

Since the perimeter is 4 sides we multiply by 4 to get 36sqrt(2) as the perimeter.

circle area = pi * radius^2

if diameter = 10 then radius = 5

circle area = pi * 5^2

circle area = pi * 25

circle area = 78.5398163397 square units

step-by-step explanation:

addition

step-by-step explanation: