En one year ago WILL MEDAL AND FAN!!! Express the surface area of a cube as a function of the length of a diagonal of one face.

1. anonymous

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2. anonymous

now we can use Pythagorus theorem one one face (Shown above)

3. anonymous

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4. anonymous

i have to leave sorry, perhaps @imqwerty can help?

5. imqwerty

ok :)

6. En

My book says that the answer is 3d^2. I dont get it :/

7. En

I know that the SA=6s^2 and the diagonal as √3 s.. idk how to go from there :/

8. imqwerty

hah XD this is not correct wait a sec i read it wrong

9. En

I keep solving it i only get 2d^2. The answer from my book is 3d^2. This is heartbreaking

10. imqwerty

|dw:1444473276715:dw|by pythagorus theorem $a^2+a^2=d^2$$2a^2=d^2$$a=\frac{ d }{ \sqrt{2} }$surface area is given by-$Area=6a^2$putting the value of a we got-$Area=6 \times \left( \frac{ d }{ \sqrt{2} } \right)^2$$Area=6 \times \frac{ d^2 }{ 2}$ $Area=3d^2$

11. anonymous

sorry, i'm back. ye well done @imqwerty