Re: DSolving(?) for a given tangent
- To: mathgroup at smc.vnet.net
- Subject: [mg82533] Re: DSolving(?) for a given tangent
- From: Peter Pein <petsie at dordos.net>
- Date: Wed, 24 Oct 2007 04:22:10 -0400 (EDT)
- References: <fct9c4$r6e$1@smc.vnet.net> <fd2fmv$s0e$1@smc.vnet.net> <ffhs2n$5md$1@smc.vnet.net>
No, he accidentally used "invisibleTan[]" ;-) Peter Jerry schrieb: > Sir, for some reason this does not work on my XP machine > using V6. I get the correct answer if I use > > In[3]:= {x, f[x]} /. First[Quiet[Solve[D[f[x], x] == 1.0, x]]] > > This gives {6.8824, 4.54545} for output. > > I'm guessing your "Degree" is different from mine which is > 0.0174533. > > Regards, Jerry > > Adriano Pascoletti wrote: >> On Sep 20, 10:01 am, "AngleWyrm" <anglew... at yahoo.com> wrote: >>> Don't know for sure if this is the right function, so here's the scenario: >>> >>> f[x_] := E^(0.22 x); >>> Plot[f[x], {x, 6, 36}] >>> >>> Which plots a nice escalating curve. >>> >>> What I would like to know is: Where is the point {x,f[x]} that has a >>> 45-degree tangent line; ie where is this curve's balance point before it >>> really starts taking off? >> In[2]:= f[x_] := E^(0.22*x); >> In[3]:= {x, f[x]} /. First[Quiet[Solve[D[f[x], x] == 45*Degree, x]]] >> >> Out[3]= {6.882398784680798, 4.545454545454546} >> >> Quiet suppresses the warning message: >> Solve::ifun:Inverse functions are being \ >> used by Solve, so some solutions may not be found; use Reduce for \ >> complete solution information. >> >> >> This verifies the result >> In[4]:= D[f[x], x]/Degree /. First[Quiet[Solve[D[f[x], x] == >> 45*Degree, x]]] >> >> Out[4]= 45. >> >> Adriano Pascoletti >> >> >