Posted by Christy on Sunday, January 12, 2014 at 6:21pm.
Express the edge length of a cube as a function of the cube's diagonal length d. Then express the surface area and volume of the cube as a function of the diagonal length.

precalculus  Steve, Sunday, January 12, 2014 at 6:31pm
d^2 = 3s^2
so, s = (d/3)^(1/2)
v = s^3 = (d/3)^(3/2)
A = 6s^2 = 2d

precalculus  Damon, Sunday, January 12, 2014 at 6:36pm
edge length s
diagonal of a side = s sqrt 2
then right triangle with legs s and s sqrt 2
d^2 = s^2 + 2 s^2 = 3 s^2
d = s sqrt 3
s = d/ sqrt 3 = d (3)^.5
area = 6s^2 = 6d^2 (3)1 = 6d^2/3 =2 d^2
vol=s^3=[d(3^.5)]^3 = d^3 /(3 sqrt 3)
= (d^3 sqrt 3)/9

precalculus  typo  Steve, Sunday, January 12, 2014 at 6:38pm
Scratch all that, since
s = d/√3
v = s^3 = d^3/√27
a = 6s^2 = 2d^2

precalculus  Damon, Sunday, January 12, 2014 at 6:40pm
whew :)

precalculus  Christy, Sunday, January 12, 2014 at 6:45pm
thank you :)
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