isolate variable
05-16-2020, 02:36 PM
Post: #1
 Davidro Junior Member Posts: 17 Joined: Dec 2013
isolate variable
Personal:

How to isolate x in equation 1/√x=2*log⁡((y*√x)-0,8), on HP Prime?
I looked in the groups and found no answers.

Grateful

Davidro
05-16-2020, 03:01 PM (This post was last modified: 05-16-2020 03:11 PM by victorvbc.)
Post: #2
 victorvbc Junior Member Posts: 46 Joined: Jun 2019
RE: isolate variable
The solution for x in this particular equation can't be expressed in terms of elementary functions. It needs the product logarithm (omega function), which the calc doesn't seem to have, so it won't be able to isolate x, unfortunately.

It can isolate y though:

Code:
 solve(1/sqrt(x)=2*ln(sqrt(x)*y-0.8),y) (e^(1/(2.*√x))+0.8)/√x
05-16-2020, 03:16 PM
Post: #3
 Davidro Junior Member Posts: 17 Joined: Dec 2013
RE: isolate variable
(05-16-2020 03:01 PM)victorvbc Wrote:  The solution for x in this particular equation can't be expressed in terms of elementary functions. It needs the product logarithm (omega function), which the calc doesn't seem to have, so it won't be able to isolate x, unfortunately.

It can isolate y though:

Code:
 solve(1/sqrt(x)=2*ln(sqrt(x)*y-0.8),y) (e^(1/(2.*√x))+0.8)/√x

Ok.,

Grateful
05-16-2020, 03:19 PM (This post was last modified: 05-16-2020 03:25 PM by victorvbc.)
Post: #4
 victorvbc Junior Member Posts: 46 Joined: Jun 2019
RE: isolate variable
Also, you can of course solve numerically (fsolve) for values of y, or graphically using the implicit plot in the advanced graphing app.

05-23-2020, 05:05 PM
Post: #5
 CyberAngel Member Posts: 283 Joined: Jul 2018
RE: isolate variable
(05-16-2020 03:01 PM)victorvbc Wrote:  The solution for x in this particular equation can't be expressed in terms of elementary functions. It needs the product logarithm (omega function), which the calc doesn't seem to have, so it won't be able to isolate x, unfortunately.
X

Lambert W (as an analytic function)
has been missing ever since HP-28C.
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