Texas Instruments TI-89 Tip List page 425

...
inputStr "enter your function in x", var1
expr(var1&"store y1(x)")
...
fMin() and fMax() are hard to use in programs.
The functions fMin() and fMax() return a list of candidate "x values" where minimums or maximums
could occur. The result is returned in the form of " x=2 or x=4 or x=19 ...". To get at the actual values
of the candidates, use the exp>list() conversion function. The exp>list() function returns the right hand
sides of the x=2 or x=4 ... (like) boolean results.
Equation for the graph on the cover of the TI-92 manual.
The equation for the graph found on the cover of the TI-92 manual is:
x 2 +y 2
20$cos
z ( x, y ) =
x 2 +y 2 +✜
WINDOW:
eyetheta = 20
eyephi = 70
xmin = -5
xmax = 5
xgrid = 20
fMin(expresn, x) and fMax(expresn, x) return only x values - why?
If you have the x values where minimums or maximums occur, then it is easy to get the expression
values at those points by using the "with" operator. If we were to return instead the expression values
that are maximum or minimum, then the corresponding x values would be lost.
expand() function algorithm
Polynomial expansion is done by repeated application of the distributive law, interleaved with use of the
associative and commutative laws to collect similar terms.
Error FOLDER when I try to copy a var in VAR-LINK why?
The copy var utility is for copying a variable to another folder, retaining the same variable name. If you
want to make a copy of a variable in the same folder you must first copy the var to another folder,
rename it, and then copy it back to the original folder.
Equation Solver on the TI-92?
The 92 doesn't have a Solver editor like the TI-85, but the TI-92 does have a more general Solve().
For example:
Solve(x^2+3y+4z=26,x)|y=2 and z=4
or symbolically
Solve(x+2y+7z=17,x)
4
ymin = -5
ymax = 5
ygrid = 20
x=-2y-7z+17
zmin = -1.2953 (approx)
zmax = 6.3662 (approx)
zscl = 1
x=2 or x=-2
B - 14