# Thread: Equation Variables (Y1 , Y2 ...) ??

1. ## Equation Variables (Y1 , Y2 ...) ??

hi,
im a bit unfamiliar with my ti89 titanium. I cant figure how to get the variables y1,y2, etc. i searched in the catalog but i coudnt find them. Before this i used to work with a ti86 and i would go to catalog> eqn> and y1,y2,.. would be thr.

thnks for ur help in advance

2. Originally Posted by omnivore
hi,
im a bit unfamiliar with my ti89 titanium. I cant figure how to get the variables y1,y2, etc. i searched in the catalog but i coudnt find them. Before this i used to work with a ti86 and i would go to catalog> eqn> and y1,y2,.. would be thr.

thnks for ur help in advance
If you have some expression in x stored in y1, you can evaluate y1 at the point c by entering
Code:
y1(c)
For example, if you go to the y= screen and set
Code:
y1=x^2
you can then do
Code:
y1(3)
>> 9
And if it isn't perfectly clear, you enter "y1" by pressing the "y" key followed by the "1" key.

Also, if you would like to store something in y1 without going to the y= screen, you can use

Code:
... -> y1(x)
where the ellipsis is an expression in x and the "->" is the variable assignment operator, obtained by pressing the "STO>" key, above the ON button. You can define and use other functions in this way, too; you are not limited to just the y's.

But the main reason i asked the question was bcoz i want to create a custom menu (i dont really like the current custom menu so ill make some changes, like bringing the nInt and nDer functions above integrate and d/dx expressions...) Most importantly though i need a menu which has the equation variables so that if ive entered an equation in the y= editor i can jus use the y1 ,y2,.. values. It helps when im doing problems that require area b/w two graphs or volume of rotations...

4. Originally Posted by omnivore
Most importantly though i need a menu which has the equation variables so that if ive entered an equation in the y= editor i can jus use the y1 ,y2,.. values. It helps when im doing problems that require area b/w two graphs or volume of rotations...
Is it really so hard to just type y1(x)? It is 5 easy key strokes.

If you like, though, you can press [2ND] [VAR-LINK], scroll down to your y variable, and press [ENTER]. But this is not nearly as convenient, unless you are dealing with custom functions with long names (and in that case, it would be easier to open the catalog and hit F4).

5. Originally Posted by Reckoner
Is it really so hard to just type y1(x)? It is 5 easy key strokes.
ll yea...i think you are right...guess ill have to adapt to the new calculator
thnks

6. Originally Posted by omnivore
ll yea...i think you are right...guess ill have to adapt to the new calculator
thnks
Well, if you need to type it repeatedly during a certain problem, then you can always copy and paste. Enter "y1(x)," press [ENTER], scroll up and highlight the input, and press [2ND] [COPY]. Then when you want to paste it, as you are typing, press [2ND] [PASTE].