ti 89 implicit differenciation

[thisongaintgottaname]

hi everyone,

does anyone know the calculator formula to solve the following problem straightaway?

find the gradient of the tangent to the curve 2(x)LN(y)-x=y at the point where y=e.

sorry, i don't really know how to use TEX so excuse the funny looking equation

your help willl be really really appreciated!!!

[TrueTears]

I don't think it can do implicit, I've tried it with /0 before, I think it treats y as a constant.

[GerrySly]

You go F3 -> D -> impDif(2*x*ln(y)-x=y,x,y)

Should give you the dy/dx, then just sub y=e into the original equation and find x, then just sub it into your equation

[/0]

Use:

impDif(Equation, independent variable, dependent variable)

E.g.


(oop Gerrysly got there)

[TrueTears]

Where do you find F3 -> D?

[/0]

F3, ALPHA, D

[Damo17]

For version 3.10 you can do as GerrySly says, but if you have (I think) version 3.01 you have do as follows:



then to implicit differentiate something:

[TrueTears]

Wow thanks, never knew that heh.

[thisongaintgottaname]

thanks guys, but how do you find the gradient after you found the x and y value and need to sub it in? do you use solve? or do you simply put x and y value, in this case, e, in to the equation?

gah,how come it doesn't work?

[Flaming_Arrow]

thanks guys, but how do you find the gradient after you found the x and y value and need to sub it in? do you use solve? or do you simply put x and y value, in this case, e, in to the equation?

gah,how come it doesn't work?

ye just sub in x and y

[thisongaintgottaname]

^_^; tyty

[TrueTears]

You can also put | x = something and y = something after your equation, saves you the trouble of pressing buttons and subbing values for x and y

[thisongaintgottaname]

You can also put | x = something and y = something after your equation, saves you the trouble of pressing buttons and subbing values for x and y

OMG that sounds familiar i think i were taught to do this but my terrible memory....@#)(*$&

do you put the |x= and | y= thing after the "impdiff()" ? and do you put an "and" between x and y?

ty tt

[Flaming_Arrow]

You can also put | x = something and y = something after your equation, saves you the trouble of pressing buttons and subbing values for x and y

ye thats what i meant by subbing in

[TrueTears]

You can also put | x = something and y = something after your equation, saves you the trouble of pressing buttons and subbing values for x and y

OMG that sounds familiar i think i were taught to do this but my terrible memory....@#)(*$&

do you put the |x= and | y= thing after the "impdiff()" ? and do you put an "and" between x and y?

ty tt

Yeap you put an "and" , you can find it in catalog