Services & Resources / Wolfram Forums / MathGroup Archive
-----

MathGroup Archive 2010

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: How can I obtain the common tangent of two curves within

  • To: mathgroup at smc.vnet.net
  • Subject: [mg114932] Re: How can I obtain the common tangent of two curves within
  • From: Peter Breitfeld <phbrf at t-online.de>
  • Date: Thu, 23 Dec 2010 03:53:48 -0500 (EST)
  • References: <ies9uk$aak$1@smc.vnet.net>

Hongyi Zhao wrote:

> Dear all,
>
> I've two curves corresponding to two functions, say, y=f_1(x),  and
> y=f_2(x).  Now, I want to obtain the common tangent of these two
> curves within mathematica? What code or commands I should use for this
> purpose?  Thanks in advance.
>
> Best regards.
>

Suppose your common tangent is g[x_]=m x+c. Then you have to solve the
system of equations:

eqns= {f1[u]==g[u],f1'[u]==m,f2[v]==g[v],f2'[v]==m}

Now solve the system:

sol=Solve[eqns,{m,c,u,v}]

g[x_]=m x+c /.sol[[1]]

-- 
_________________________________________________________________
Peter Breitfeld, Bad Saulgau, Germany -- http://www.pBreitfeld.de


  • Prev by Date: 2 obvious
  • Next by Date: Re: what's wrong with this?!!
  • Previous by thread: How can I obtain the common tangent of two curves within
  • Next by thread: Median filter