Solving the Preliminary Example
continued fromÌýlast page...)
Your little session should look like this:
D[x[t]/.x[t]->E^(-t),t]
Now remember, this is the value of theÌýleft hand sideÌýof the first equation. To complete our verification of the proposed solution we have a lot more work to do. (Three more commands, in fact, since there are four "sides" in all.)
Since we're on a new page, let me remind you again of the problem and proposed solution.
| Problem | Proposed Solution | |
|---|---|---|
| (1) | x'Ìý=ÌýyÌý-ÌýxÌý-Ìýe3t | x(t) =Ìýe-Ìýt |
| (2) | y'Ìý= 3yÌý+ 2xÌý- 2e-Ìýt | y(t) =Ìýe3t |
As we said a moment ago, so far we have verified the value of the left hand side of the first equation. We must now check it's right hand side.
The command we need to substitute both theÌýx(t) andÌýy(t) value into the right hand side of equation (1) is:
y[t]-x[t]-E^(3t)/.{x[t]->E^(-t),y[t]->E^(3t)}
Jump back toÌýMathematicaÌýand try it. (Remember, you can "cheat" on the typing by usingÌýCopyÌý²¹²Ô»åÌýPaste.)
°Â±ð'±ô±ôÌýnow seeÌýwhat you should have gotten...
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