Author 
Comment/Response 
Brett

06/20/13 03:23am
Hi,
I have a problem for which I'm using Solve to first solve a system of three equations, so I get a list of three solutions. So far, so good. Now I'd like to use one of the solutions in another Solve statement to solve for another variable. The code I've tried is below. I don't get how to pick out one of the previous Solve solutions and insert it into another Solve function.
My first solve is as follows:
Solve[{(1/2) k d^2 + m g (el + d) Sin[q] ==
m g el Sin[q] + (1/2) m v^2 + (1/2) ii w^2, ii == (1/2) m r^2,
v == w r}, {v, w, ii}]
I get list of three solutions. I'm interested in the first (v). I now want to plug this solution for v into another equation and solve analytically for u. I tried the following (but got an error):
Solve[{m g el Sin[q] + (1/2) m v^2 ==
m g (el/2) Sin[q] + (1/2) m u^2 + (1/2) k (el/2)^2, %3[[2]][[1]]}, {u, m}]
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