MaplePrimes - answers and comments on Question, Plotting Function

Need to deal with the constants of integration

Carl Love — Mon, 18 Mar 2013 21:21:27 Z

Before you can plot it, you need to deal with the six constants of integration _C1, ..., _C6. Can you find six initial or boundary conditions?

eval(x(t), ...)

Carl Love — Sat, 30 Mar 2013 04:09:13 Z

Assign the solution given by dsolve to a variable:

soln:= dsolve(..., x(t));

where you have to substitute your actual dsolve command. Then, to plot it, do

plot(eval(x(t), soln), t= 0..10);

If this doesn't work for you, please post or upload your code!

how to determine the constants of integration

shorty101 — Tue, 19 Mar 2013 14:05:45 Z

Ah I see.

How would one determine these?

Cause I use maple to assist with this?

Initial conditions

Carl Love — Tue, 19 Mar 2013 18:26:29 Z

@shorty101

> How would one determine these?

There has to be some context in the original problem for them. For example, if a problem says "A gun is fired straight up from a height of 10 m with an initial velocity of 500 m/s. What is the height H(t) of the projectile at time t?" then the initial conditions are H(0) = 10 and H'(0) = 500.

> Cause I use maple to assist with this?

Once you determine the initial conditions, Maple can help with solving for the constants.

You should post the entire original problem and your call to dsolve. It's hard to believe that you are dealing with Mathieu functions with three parameters and six constants of integration and yet you had to ask those two questions. So my guess is that you've entered the problem incorrectly into dsolve.

@Carl Love You're right. entered

shorty101 — Thu, 28 Mar 2013 14:33:18 Z

@Carl Love

You're right. entered my equation worng. Thanks

@Carl Love Nevertheless,If we were

shorty101 — Thu, 28 Mar 2013 15:09:45 Z

@Carl Love

Nevertheless,

If we were to say that:
_C3 := 0.5;
_C4 := 0;

b := 0.8;
g := 2000000;
e := 2.8;

In the range of t from 0 to say 10. I am still unable to plot this function for x(t).

Any reason as to why this may be?


I do the call (after running dsolve and setting all the values for the variables):
plot(x(t), t = 0 .. 10)

I just get:
Warning, unable to evaluate the function to numeric values in the region; see the plotting command's help page to ensure the calling sequence is correct

With an empty graph displayed also.

I would be sooo thankful for any help!!