15-Moonstone

Solved

Symbolic derivative

Forum|Forum|7 years ago
June 4, 2019
16 replies
6430 views

Hello,

I am trying to evaluate the derivative of a function symbolically.

Would anybody, please, help me with this issue?

Best regards,

Sergey

1_Undamped-motion.zip

Calculus_Derivatives

Best answer by LucMeekes

You have to define x(t), that is, use ': ' to get ':=', not set it as a boolean (bold =),.

Success!

Luc

-

-MFra-

21-Topaz II

Hi,

before the symbolic derivative you must use clear(A), clear(B), clear(t), clear(omega) or also clear(A,B,t,omega), furthermore you have to use the definition symbol " : " for the function definition and not the equal to "=", as Luc says in his post.

S

Sergey

Author

15-Moonstone

Hello,

Thanks for reply.

As long as I can see, it doesn't work.

Would you please use my .mcdx file and apply your suggestion properly?

Sergey

1_Undamped-motion_clear.zip

L

LucMeekes

Answer

23-Emerald IV

You have to define x(t), that is, use ': ' to get ':=', not set it as a boolean (bold =),.

Success!

Luc

S

Sergey

Author

15-Moonstone

Hei,

I used "clear (A)" and then defined "x(t)" as you advised. It worked.

Mathcad's results are complying with my beforehand calculated values.

Thanks a lot.

Best regards,

Sergey

W

Werner_E

25-Diamond I

If your goal is to find the derivative but use the value of B you defined and the value of A you found using the solve block, the attached sheet should help.

What had to be changed:

1) B (and possibly x, which later is overwritten by function x) should be defined outside of the solve block

2) no need for x=1 in the solve bock as x IS 1

3) clear variable t (at least for symbolics) - you don't want it to be 0s anymore

4) Make the result of the solve block usable for the symbolics by using the inline evaluation "trick"

2_WE_20190604_Undamped-motion-1.zip