I need some help with AP CALC problem

[TeenZone]

Question-

Write a formula that expresses the first variable as a function of the second:

1. the area of a circle as a function of its diameter
2. the surface area of a cube as a function of the length of the cube's edges



*I have the answers from the back of the book, but I don't know they arrived at them.

Answer: 1. A=piDsquared/4
2. S=6esquared

 

[stapel]

1) What is the area formula for a circle? How does the radius r relate to the diameter d?

2) What is the surface-area formula for a cube with edges of length s?

Eliz.

 

[Guest]

area = pi (r)^2

but r= d/2

then.. (r)^2 = (d/2)^2
=(d^2)/4

now use this is the original formula....