I'm having massive difficulty in rearranging the following to find d

c/h=(d^2)*[1-exp-(2r^2/d^2)]

taking the natural log of both sides normally helps when there is an exp function present but here it just gets in the way - no matter how hard I try I can't get d on its own (d in terms of c and r).

can anyone help?

showing the steps you took would help me tackle similar problems in the future so I'd be extremely grateful for this.

Dan

2. There is no Algebra I method to solve such things.

Have a look at Lambert's W-Function. This will suggest to you various methods that have been contemplated to deal with such structures.

Lambert W-Function -- from Wolfram MathWorld
Lambert W function - Wikipedia, the free encyclopedia
Lambert's W-Function

On the other hand, if you do not already know of the difficulty of solving what you attempted to solve, these discussions may not suggest much that you will find useful.

On still another hand, have you considered what happens as 'd' increases without bound? $\frac{c}{h} = -2r^{2}$ Does that lead to anything useful?

On yet another hand, after substituting $q = \frac{1}{d^{2}}$ and rearranging, we have $\frac{cq}{h} = 1-e^{2qr^{2}}$

...and we can contemplate what happens for q = 0.

3. ## Thanks

Many thanks for such a comprehensive reply. It's beyond the scope of my current level of understanding but i'll endevour to fill in the blanks by doing some background reading.

Thanks once again

Dan