Mathematics & Science Learning Center
Computer Laboratory

Applications of Differential Equations

A Suspended Wire

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Your Mathematica session should have gone something like this:

ansol=DSolve[{y''[x]==(0.5/40)*Sqrt[1+(y'[x])^2], y[0]==0, y'[0]==0}, y[x], x]

Solve::ifun: Inverse functions are being used by Solve, so some solutions may not be found; use Reduce for complete solution information. >>

Mathematica produces three solutions, though two of them appear to be complex, since they involve the imaginary constant, i. Since we're only interested in real solutions, the first solution listed is the one we wish to extract from this set. This may be done by using what may be called, the "[[1,1,2]] trick."

Use it now, by issuing the command:

ansol1 = ansol[[1, 1, 2]]

Let's go and see what you should have gotten...

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