Solving rotation of conics on the Prime? Is there perhaps a better way?
09-09-2015, 04:11 PM (This post was last modified: 09-09-2015 05:23 PM by pwarmuth.)
Post: #1
 pwarmuth Junior Member Posts: 35 Joined: Sep 2015
Solving rotation of conics on the Prime? Is there perhaps a better way?
I would like to know if there is a better way to do this on the HP prime. Is there a built in function or something I can use to simplify this process, besides writing a custom program? It's so tedious.

Transform the equation in x and y into an equation in X and Y (without an XY-term) by rotating the x- and y-axes by the indicated angle. I am using the Prime to verify my answers.
Problem: y^2 -sqrt(3)*x*y + 3 = 0 where theta is 30 degrees.

For reference: x=x, y=y, a=X', b=Y' and c=theta

[CAS]
[set degree mode]
x:=a*cos(c)-b*sin(c)
y:=a*sin(c)+b*cos(c)
c:=30

then use the stored variables to evaluate the equation that I'm working with.

y^2-sqrt(3)*x*y+3=0

That input simplifies to

[(-a)^2+3b^2+6]/2=0

Takes a little more manual transformation to get it into the standard form of a hyperbola, and I arrive then at the correct answer:

[(a^2)/6] -[(b^2)/2] = 1 where a = x and b=y.
01-17-2018, 03:40 AM
Post: #2
 math7 Member Posts: 163 Joined: Feb 2017
RE: Solving rotation of conics on the Prime? Is there perhaps a better way?
definitely the HP Prime needs a conic application, if I could program to the required level I would but I do not have that knowledge...
01-19-2018, 10:13 AM
Post: #3
 parisse Senior Member Posts: 1,013 Joined: Dec 2013
RE: Solving rotation of conics on the Prime? Is there perhaps a better way?
Giac has a command to find the center, axis of a conic and return the reduced equations: it's reduced_conic. Maybe it's in the public beta.
01-19-2018, 10:16 AM
Post: #4
 salvomic Senior Member Posts: 1,364 Joined: Jan 2015
RE: Solving rotation of conics on the Prime? Is there perhaps a better way?
(01-19-2018 10:13 AM)parisse Wrote:  Giac has a command to find the center, axis of a conic and return the reduced equations: it's reduced_conic. Maybe it's in the public beta.

yes, it is already in the beta v3:
Code:
reduced_conic(Expr,[Vector])

Salvo

∫aL√0mic (IT9CLU), HP Prime 50g 41CX 71b 42s 12C 15C - DM42 WP34s :: Prime Soft. Lib
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