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