Mathematica 9 is now available
Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
2001
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*November
*December
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 2001

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

Search the Archive

What is the difference between z[x_]:= D[y[x],x] and z[x_]:=y'[x]?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg27436] What is the difference between z[x_]:= D[y[x],x] and z[x_]:=y'[x]?
  • From: liwen liwen <gzgear at yahoo.com>
  • Date: Sun, 25 Feb 2001 20:55:39 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

Dear friends,
How are you!
I want to know the difference between z[x_]:=
D[y[x],x] and z[x_]:=y'[x].

Also,I want to why I can not find the answer for the
u[0.5] by the following routine:

(r1[t_] = 93/(1 + 0.12*Cos[3*t]);
  d1[t_] := ArcTan[r1[t]/D[r1[t], t]];
  Block[{t}, u[t_] := If[(Pi/3 >= t > 0), d1[t]]];
  )

u[0.5]
General::"ivar": "\!\(0.5`\) is not a valid variable."

But it is available by the following routine:

(r1[t_] = 93/(1 + 0.12*Cos[3*t]);
  d1[t_] = ArcTan[r1[t]/D[r1[t], t]];
  Block[{t}, u[t_] := If[(Pi/3 >= t > 0), d1[t]]];
  )

u[0.5]
1.22872
(* ------------------------ *)

Please help.

Bets Regards,


Liwen  2/26/2001

E-mail: gzgear at yahoo.com

__________________________________________________
Do You Yahoo!?
Get email at your own domain with Yahoo! Mail. 
http://personal.mail.yahoo.com/


  • Prev by Date: Re: Plot[(1 + 10^(-k))^(10^k), {k, 2, 9}]
  • Next by Date: Re: Deriviation d/dt(x(t))
  • Previous by thread: Re: Integrate a matrix-function
  • Next by thread: Re: What is the difference between z[x_]:= D[y[x],x] and z[x_]:=y'[x]?