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lvl10720-Turquoise
20-Turquoise
October 23, 2018
Solved

x.cos(x) - sin(x) = 0 solve , x ?

  • October 23, 2018
  • 4 replies
  • 10585 views

  Hello, Everyone.

  x.cos(x) - sin(x) = 0 solve , x ?

  x.cos(x) - sin(x) = 0 solve , x .PNG

     Thanks in advance.

           Regards.

Best answer by Werner_E

 

B.PNG

 

4 replies

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LucMeekes23-Emerald IV
23-Emerald IV
October 23, 2018

Is related to solving tan(x)-x=0:

LM_20181023_xcos(x)-sin(x).png

You should be able to find local zeros using the bracketed root function:

root(x*cos(x)-sin(x),-1,1)=

root(x*cos(x)-sin(x),-5,-4)=

etc.

 

Success!
Luc

 

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Werner_E25-Diamond I
25-Diamond I
October 23, 2018

The symbolic "solve" will give you just the only exact solution (0).

All the others you'll have to find one by one using one of the numerical methods provided by Mathcad (solve block, root).

W
Werner_E25-Diamond IAnswer
25-Diamond I
October 23, 2018

 

B.PNG

 

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lvl10720-TurquoiseAuthor
20-Turquoise
October 24, 2018

   Many thanks Luc, F.M., and Werner. Smiley HappySmiley Happy. Werner, I have a related issue, if you don't mind, please make correction the program function for a simple case :

( I-a ).PNG

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-MFra-21-Topaz II
21-Topaz II
October 23, 2018

Hi liv107,

since it is a transcendent equation, you can solve it only numerically.

 

transcendent eq.jpg

V
24-Ruby IV
ValeryOchkov24-Ruby IV
24-Ruby IV
October 24, 2018

More roots - not free

Roots.png

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