Betts 10 73 74

[Peter230655]

These two simulations solve the same problem, but formulated differently. This may be a candidate for examples-gallery for these reasons:

• Problem 10.73 has a boundary condition at the end of the interval as function(state variables, parameters) = 0 As opty does not presently allow such instance constraints, I introduced a new state variable hilfs and an additional equation of motion: hilfs - function(state variables, parameters) = 0. Then I set the instance constraint hilfs($t_f$) = 0 . I do not think, there is such an example in examples-gallery.
• Without very good initial conditions, I could not get 10.73 to converge, while 10.74 converged very rapidly. Hence equivalent formulations may make difference on how well the problem can be solved.

[Peter230655]

Something went wrong. I close this PR