I am trying to graph r=sqroot(sin2theta) on my ti-89 titanium in polar mode and it is telling me when i try to graph that there is an undefined variable. what do i do?

Hard Reset means reset. Everything gone and no way to recover it.

There is no DiagnosticsOn command in the TI 89 Titanium. The command exists on the TI83/84PLUS where it displays the r and r^2 coefficients. On the TI89 , the correlation coefficient and the determination coefficient (r, r^2) are displayed by default among the statistics if THE REGRESSION MODEL includes them. If they are not defined by the regression model they will not be displayed. In short, you do not have to turn diagnostics ON.

Just a suggestion to you the expert.
You found a neat way to do something? Then write a TIP, clearly labeled so that people in need of this information will be able to find it.
It serves no purpose to pretend to ask a question and then answer it yourself. A TIP or HOW TO writeup will be the perfect venue for such a thing.
Sorry, I just did not want this illuminating procedure of yours to stay in the dark.

Enter a function in Y= Editor, then draw its graph.



While the graph is still displayed Press F1



Press 9:Format to open the FORMAT screen


Toggle the Axes ON

If you want to graph the absolute value of a function, feed the function to the absolute value ie graph y= abs(f(x)). The calculator will take care of it. See screen captures where I draw the function y1=x^3-5x^2-3 and y2='x^3-5x^2-3'. On the first graph the function is represented and on the second the function and its absolute value.







The calculator knows how to calculate the absolute value of an expression. The name of the command is abs(

I am aware that this does not fully answer your WHY question but it may help you decide what to do.
On the TI92 Plus, which has the latest OS for that machine 2.09 Advanced mathematics Software one gets the result Pi in EXACT or AUTO modes and 3.1415926536 in APPROXIMATE mode.
However when in EXACT/AUTO mode the calculator displays a warning message Memory Full, Simplification may Not Be Complete. (see screen capture.)


On the Voyage 200 PLT with OS version 3, the same as on the Titanium (not Platinum), I get an undefined result in EXACT MODE and 3.1415926536 in APPROXIMATE MODE.



So you can get the approximate value of the integral on the Titanium or the indefinite integral which you can evaluate between the two boundary points.

Set your calculator to RAD mode and then graphing functions.
See example for y=sin x

You have your angular mode set to degrees. Ten degrees is about 0.17 radians, and for small x: sin(x) is nearly equal to x. Thus, sin(x) from -10 to 10 is indeed nearly a straight diagonal line.

Press MODE, then scroll down to "Angle" to change the angular mode.

That means one (or more) of the variables you have in your function is not defined. Check to make sure you didn't misspell any variable name. Also, check to make sure you didn't run two variable names together. "ab" is the variable ab, not a times b.

I have a TI-89 Titanium and I have experienced the same problem. HERE IS HOW TO FIX IT:

Goto " MODE " and scroll down the options until you get to
" COMPLEX FORMAT " change that option to " RECTANGULAR " and press ENTER until you exit out of the " MODE " screen. (very important that you press ' enter ' until you exit because if you don't, it will not save your changes. )