Re: FindRoot vs Solve
- To: mathgroup at smc.vnet.net
- Subject: [mg22507] Re: FindRoot vs Solve
- From: "Bill Bertram" <wkb at ansto.gov.au>
- Date: Sat, 4 Mar 2000 02:27:08 -0500 (EST)
- Organization: Australian Nuclear Science and Technology Organisation
- References: <89ichk$n45@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
F. Mittermayr wrote in message <89ichk$n45 at smc.vnet.net>...
>Why is FindRoot not able to solve an equation using "Degree"? Solve can do
>it.
>
>In[]=
>
>Solve[28. Cos[phi Degree] - 20. == 0, phi]
>FindRoot[28. Cos[phi1 Degree] - 20. == 0, {phi1, 0.1, 0.1, 90.}]
>
>Out[]=
>
>{{phi->-44.4153},{phi->44.4153}}
>{phi1->96.7112}
Dear F.
FindRoot does work provided you give an appropriate initial guess for phi1.
Try for example
FindRoot[28. Cos[phi1 Degree] - 20. == 0, {phi1, 20, 0.1,
90.}]
and you'll find it gives the correct solution.
Cheers,
Bill