Re: Re: Mathematica can't win against Tiger Woods
- To: mathgroup at smc.vnet.net
- Subject: [mg19810] Re: [mg19765] Re: [mg19677] Mathematica can't win against Tiger Woods
- From: BobHanlon at aol.com
- Date: Fri, 17 Sep 1999 01:36:53 -0400
- Sender: owner-wri-mathgroup at wolfram.com
Leszek,
soln1 = Solve[{p == b^2/a, e == Sqrt[a^2 - b^2]/a}, {a, b}];
Since you know that b > 0,
soln = Select[soln1, Simplify[(b /. #) > 0, {p > 0, 0 <= e < 1}] &] //
Flatten;
soln // InputForm
{b -> (I*p)/Sqrt[-1 + e^2], a -> -(p/(-1 + e^2))}
Look at the FullForm of the expression for b
FullForm[b /. soln]
Times[Complex[0, 1], Power[Plus[-1, Power[e, 2]], Rational[-1, 2]], p]
Replace the form that you want changed
soln /. Power[x_, Rational[-1, 2]] :>
-I*Power[-x, Rational[-1, 2]] // InputForm
{b -> p/Sqrt[1 - e^2], a -> -(p/(-1 + e^2))}
I would rather explain the concept of I to a high school class than
semi-latus rectum.
Bob Hanlon