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W
Werner_E25-Diamond I
25-Diamond I
December 13, 2024

According to the error message Prime expects initial conditions for alpha and beta, even though there is no ODE for these functions

Werner_E_1-1734084972009.png

 

According the second approach and the m^2.

I am not sure if this is as it should be (a bug?) but we get the correct result if the initial value is just 0 or Zero (capital Z. no lower case).
I tend to call it a bug. As the derivative (D, tan) is dimensionless, the solution must be of the same dimension as x and the same applies to the initial value.

Werner_E_1-1734086602007.png

Limiting the vector x to values between 0m and 1m was necessary because its last value was very slightly (about 10^-16) larger than 1m and so the function y would fail.

 

 

 

S
StuartBruff23-Emerald V
23-Emerald V
December 15, 2024
@Werner_E wrote:

I am not sure if this is as it should be (a bug?) but we get the correct result if the initial value is just 0 or Zero (capital Z. no lower case).
I tend to call it a bug. As the derivative (D, tan) is dimensionless, the solution must be of the same dimension as x and the same applies to the initial value.

@ValeryOchkov @AlanStevens 

It is informative to try different numerical integrators.

 

2024 12 15 A.png

 

Of course, one could always roll one's own integrator.  Here's one I prepared earlier that runs (ran) under Mathcad Prime Express 7. 

 

(I've got a programmed version somewhere of the Runge-Kutta and Adams-Moulton predictor-corrector families that I wrote for M11, but I can't find it at the moment)

 

2024 12 15 B.png

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