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Student Support Forum: 'using result of previous Solve in another Solve' topicStudent Support Forum > General > "using result of previous Solve in another Solve"

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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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Subject (listing for 'using result of previous Solve in another Solve')
Author Date Posted
using result of previous Solve in another Solve Brett 06/20/13 03:23am
Re: using result of previous Solve in another S... Bill Simpson 06/20/13 3:09pm
Re: Re: using result of previous Solve in anoth... Brett 06/20/13 9:06pm
Re: Re: Re: using result of previous Solve in a... Bill Simpson 06/21/13 02:08am
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