Odesolve plot notable differences

[JW_9781974]

The plot is changing enormously when ode solve is used. Any suggestions? 

[Werner_E]

odesolve divides the interval by default into 10^3 steps.

If the interval runs from 0 to 6 as in your first example, this means timestep is 0.006

But if you increase the interval by the factor 500 as in your last example (t runs from 0 to 3000), the timestep increases by the same factor and is now 3. Of course this usually yields a very inaccurate result.

Solution could be to increase the default value of 10^3 steps - its the fourth (optional) argument of the odesolve function.

Feel free to increase the value significantly more for more precision at the higher values of t.

[JW_9781974]

I tried and it worked however, it is not working with the other equations does this needs to be changed? 

[Werner_E]

My best guess is that you confuse milliseconds with seconds and you don't see it because no units are used.

When you solve your ODEs or you draw cos(20+0.01t), what do you expect to see?

I also don't see a peak at 22,6 here - where do you see that value?

Furthermore the result is much to imprecise because of the far too small numer of steps vs. the large interval from 0 to 200

here is a more precise result

Can't be clearly seen as its definitly a high frequency signal.

Again, maybe you meant 0.2 and not 200 for the end value (milliseconds instead of seconds) ?

[LucMeekes]

I guess you (want to) know that the solution to your ode is:

M(t) = cos (t*√3) + √(4/3) * sin(t*√3).

Success!
Luc

[ttokoro]

As already masters say, it needs number 10^4.