Re: DSolving(?) for a given tangent

*To*: mathgroup at smc.vnet.net*Subject*: [mg82504] Re: DSolving(?) for a given tangent*From*: Jerry <JLK2941 at yahoo.com>*Date*: Mon, 22 Oct 2007 05:44:50 -0400 (EDT)*References*: <fct9c4$r6e$1@smc.vnet.net> <fd2fmv$s0e$1@smc.vnet.net>

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 > >