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.

Massive thanks in advance.

Dan