15c SOLVE question on usage

[Dieter]

(05-01-2014 02:24 AM)lemontea Wrote:  Can I enter an equation, say Ohm's Law, and have it solve for the 3rd unknown, if I have 2 of the 3 variables?
...
So, can I write an equation in programming, such as

(I* R) - E = 0

(or however one should program it in)

and use SOLVE to find the unknown?

Yes, I know, this is a 15C thread, but this example shows very nicely how elegantly this kind of problem is handled by newer calculators with equation solvers. For instance the 35s. Simply enter E = I x R as you write it down on paper and then solve for E, I or R. Since every variable appears only one, you do not even have to provide an initial guess - the 35s "knows" that I = E : R and R = E : I and returns the third value immediately after you have been prompted for the two others.

Of course this also works with the other example: f(x, y, z) = 2x – ln y + 1/z:

Code:

2*X - LN(Y) + 1/Z = 0

SOLVE X
Y? 15,1 R/S
Z?  5,3 R/S
X=  1,26300774927

SOLVE Y
X?  0,7 R/S
Z?  3,3 R/S
Y=  5,49056026941

The results are returned immediately as the 35s knows that x = (ln y – 1/z)/2   resp.   y = e^2x + 1/z resp.   z = 1/(ln y – 2x).

Great, huh ?-)

Dieter