finding the corresponding x value given the y value for a point using CAS?

[Nomvalt]

I'm just wondering, with the CAS calculator, you know how when you go to the Graphs and Geometry section?...and you draw a graph...you can find any y value given that you know the corresponding x value by pressing menu, trace and graph trace. Well, using the same buttons would we be able to determine the x value of a point given that we know the corresponding y coordinate for that point.

Just curious, as it might come in handy one day if so...

[m@tty]

I don't know about CAS, but with the Ti-84 the only way was to graph the line y=a, where a is the value you are looking for, then using the "intersection" function..

[luken93]

I'm just wondering, with the CAS calculator, you know how when you go to the Graphs and Geometry section?...and you draw a graph...you can find any y value given that you know the corresponding x value by pressing menu, trace and graph trace. Well, using the same buttons would we be able to determine the x value of a point given that we know the corresponding y coordinate for that point.

Just curious, as it might come in handy one day if so...

are you saying you want to know the value of x when you have a y value?
If so, not that i know of, I would sub it into the equation
orr.... you can use the table of values and scroll down to the corresponding value

[coletrain]

I'm just wondering, with the CAS calculator, you know how when you go to the Graphs and Geometry section?...and you draw a graph...you can find any y value given that you know the corresponding x value by pressing menu, trace and graph trace. Well, using the same buttons would we be able to determine the x value of a point given that we know the corresponding y coordinate for that point.

Just curious, as it might come in handy one day if so...

are you saying you want to know the value of x when you have a y value?
If so, not that i know of, I would sub it into the equation
orr.... you can use the table of values and scroll down to the corresponding value

im pretty sure these are the only ways to do it

[the.watchman]

I'm just wondering, with the CAS calculator, you know how when you go to the Graphs and Geometry section?...and you draw a graph...you can find any y value given that you know the corresponding x value by pressing menu, trace and graph trace. Well, using the same buttons would we be able to determine the x value of a point given that we know the corresponding y coordinate for that point.

Just curious, as it might come in handy one day if so...

are you saying you want to know the value of x when you have a y value?
If so, not that i know of, I would sub it into the equation
orr.... you can use the table of values and scroll down to the corresponding value

im pretty sure these are the only ways to do it

Probably the 'best' way to do it is what m@tty said, to draw the line of the y-value wanted and find the intersection point(s). It will even jump straight to that point for you

[Blakhitman]

Of course you can do that!

Use the point on function: menu --> Points & lines --> Point on

chuck a point wherever on the graph, then scroll over the y coordinate, when it says text, click it and put any y -coord you want and it will jump to that point.

Assuming you use Ti-nspire.

[Blakhitman]

remember to press escape after chucking on the point, then I think you need to press the y coord twice...

Just realised double post and on mobile so CBF doing anything about it!

[Hongld]

For CAS, what I do is generally:
- graph trace
- press enter (twice) so the point stays on
- press escape for the arrow
- use your pad to move to the y value
- double click on the y value
throw in the y value for which you want to find the corresponding x value
-  press enter and the new point should show up with that (x,y) coordinate.

 I've been doing this since last year Hope it helps.