Hi Folks,(adsbygoogle = window.adsbygoogle || []).push({});

I'm working through a pre-selection maths course and have come to a complete halt with the following Differentiation problem:-

" If the strength of a rectangular beam of wood varies as its breadth and the square of its depth, find the dimensions of the strongest beam that can be cut out of a round log, diameter d. "

It's the only problem in the notes that has more than 1 variable and no example to show how its done.

Here's what I've come up with so far....

S varies with Breadth, therefore S=kB

S varies with Depth^2, therefore S=kD^2

S=kBD^2

The derivative of a constant term = 0

If I could work out the formula I think I'd be ok, but I'm completely at a loss for what to do next.

Thanks for any help you can give me, and sorry it's a little basic.

Shipscat

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# Working out a formula for 2 variables?

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