Hi again Kath;
According to my college physics professor, E=mc2 is an over-simplification of the mathematical formula. The way E=mc2 has been taught in the grammar schools drove him crazy.
Unfortunately, I no longer have my college notes. I researched this on the internet. In its original form, the formula is ...
E=energy of the particle
p=momentum, also represented as mass multiplied by velocity, (mass)(velocity), p=mv.
c=speed of light, 299,792,458 meters per second.
If the mass is not moving, then p, momentum, is zero, because velocity (speed and direction of motion) is zero...
Then this is...
The square root of both sides is...
As William explained, this can also be represented as...
c=√(E/m) or c=(E/m)½
As to the original equation, I do not know of any way of isolating c as the subject.
I know this does not answer your question. I just want to ask of you not to drive your college professors crazy.