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##### TI-BASIC / Finding local max, min, and saddle point
« on: June 07, 2013, 01:47:56 pm »

Define sela()=
Prgm
:Local f,fx,fy,mat,fxx,fyy,a,fxxpo

©fx-> first derivative in terms of X
©fy-> first derivative in terms of Y
©mat->Trying to make extraction of coordinate point (x,y) to use in second derivative in terms of X with P0(x,y), doesnt work! Accept suggestion

©fxx and fyy second derivative in terms of respective var

©a to store coordinate point I really need HELP here! How can I use or put this two points in two different variables?

:Request "Function",f
:fx:=d/dx(f,x)
:fy:=d/dy(f,y)
:fxx:=d/dx(fx,x)
:fyy:=d/dy(fy,y)

:a:=solve(system(fx=0,fy=0),{x,y})

:fxxpo:=solve(fxx=0,x)|a

©Ok! i believe inst a good solution here if a get a "a" like this: x=−1 and y=−1 or x=0 and y=0 or x=1 and y=1 What im gonna do?

:mat:=newMat(1,2)
:mat[1,1]:=fx ©Make a new line for description
:mat[1,2]:=fy
Disp fx
Disp fy
Disp mat
Disp fxx
Disp fyy
Disp a
Disp fxxpo
Disp x
Disp y
:
:EndPrgm

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