@acer Thanks! this is spot-on. I understand my problem was quite simple, and I could have googled it however I didn't have the vocabulary to do so. Thanks for having the patience to answer :)

@mehdi jafari Thanks so much - this actually better solves my next problem (finding transmission probability). I am really new to Maple and have not had a lot of information/programming experience. Would you reccomend a similar approach for yielding the relationship;

A + R = B + C 

Or would you do the following;

x := 0: cond_1 := psi[1] = psi[2];

which yields;
A + R = B + C

I hope that's clear.

@Preben Alsholm I think what you did is more complex than what I'm trying to do. For my problem,

 A*cos(x)+ R*i*sin(x) = B*exp(-x)+ C*exp(x), when x = 0. I want to be able to solve this for the constants A, R, B and C however, I don't want the worksheet to keep x at 0, because I have to do this sort of thing for different values of x. 

I'd thought of resetting the value of x by using the command x := 'x', but that means that I cannot use the relationship that i attained through the above evaluation...

Any ideas?