Answer with explanation:
Given : The diameter of the circle = 2r , where r is the radius.
Function notation for diameter :

If the value of r= 5 feet
Then , the diameter of the circle is feet = 2(5) feet = 10 feet
Hence, the diameter of the circle is 10 feet when the radius is 5 feet.
Also, area of circle :
, where r is the radius .
Function notation for area :

For r= 5 feet


Hence, The area of the circle is
square feet when the radius is 5 feet.
Also, the circumference of circle =

Function notation for circumference =

For r= 5 feet

Hence, The circumference of the circle is
feet when the radius is feet.