Using the Equation Library on 50g

[matalog]

Using the Equation Library on a 50g, how can I ensure that the units will show in the results, like page 19-3 of the 50g manual (edition 1).

As I follow the instructions in the manual, I do not see m/s in my answer. It is actually negative 25.44 that I get, with no mention of units.

[matalog]

I didn't have the Units soft menu selected. I'm getting the results in units now but the result is still negative.

[Marco Polo]

(07-26-2022 08:19 PM)matalog Wrote:  I didn't have the Units soft menu selected. I'm getting the results in units now but the result is still negative.

If equations are correct, than wrong result came from wrong data ;-)

[matalog]

(07-27-2022 07:26 AM)Marco Polo Wrote:  

(07-26-2022 08:19 PM)matalog Wrote:  I didn't have the Units soft menu selected. I'm getting the results in units now but the result is still negative.

If equations are correct, than wrong result came from wrong data ;-)

I have gotten different results from entering the same data, it seems.

I tried the same thing again later, and it ended up being positive. Upon calculatiing the solution the calculator flashed up something about Reversal on screen. I'm not sure what that was.

When I was getting the negative reault, I went through all of my variable inputs and none were negative, for that projectile motion example, so the result shouldn't have been negative.

[cdmackay]

Can you give an example, please?

Remember that velocity is a vector, and will have the opposite sign in opposite directions, e.g. going up vs coming down.

Sign Reversal tells you that the calculator identified a root (solution) by noting where the function value changed sign, as it varied the unknown variable. The alternative root types are zero, or extremum.

Sign Reversal is when the function had values either side of zero, for two adjacent values of the unknown variable. The root/solution will be between those two values.

Zero is when the function value was zero, for a particular value of the unknown variable, which will be the root/solution.

Extremum is when the function value is a maximum or minimum, rather than at or near zero.

[Nigel (UK)]

(07-27-2022 11:11 AM)matalog Wrote:  

(07-27-2022 07:26 AM)Marco Polo Wrote:  If equations are correct, than wrong result came from wrong data ;-)

I have gotten different results from entering the same data, it seems.

I tried the same thing again later, and it ended up being positive. Upon calculatiing the solution the calculator flashed up something about Reversal on screen. I'm not sure what that was.

When I was getting the negative reault, I went through all of my variable inputs and none were negative, for that projectile motion example, so the result shouldn't have been negative.

For example, if you are solving for \(v\) given \(u\), \(a\), and \(s\), the equation \(v^2=u^2+2as\) will give both a negative and positive value for \(v\). Which one the solver returns will depend on the value already stored in \(v\); storing different values will start the search for the root from a different place, and may lead to a different answer.

This is only an example - I don't know what problem you are solving. But it isn't necessarily strange that a negative root is returned when all inputs are positive, nor that the same inputs lead to a different root on a different occasion.

Nigel (UK)