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J
jst1251-Visitor
1-Visitor
April 2, 2019
Solved

Using a solve block with a vector equation

  • April 2, 2019
  • 3 replies
  • 2941 views

Hi,

 

I get a "No Solution is found" from the find() in this solve block in Mathcad prime.  Can someone please tell me where I'm going wrong?  (code attached)

 

I have noticed that if i put the initial guess in for 'h' as the answer then the solve works but this defeats the object somewhat.

 

Thanks in advance!

Best answer by terryhendicott

Hi,

 

Have included solving for the root of an equation for you.

Cheers

Terry

3 replies

T
21-Topaz II
terryhendicott21-Topaz II
21-Topaz II
April 3, 2019

Hi,

 

It helps to plot the function to see what is happening and why it cannot solve.

First write a function of "h" to plot.

Capture.PNG

Then plot the function foo.

Capture-2.PNG

V
24-Ruby IV
ValeryOchkov24-Ruby IV
24-Ruby IV
April 3, 2019

There are three good rules when working with a block Solve.
1. Before solving the equation in vector form - solve it in scalar form
2. Before Solving Inequality (>=, <= etc) - Solve Equality (=)
3. If you have one equation, not several, then use not a block Solve, but a function root

T
21-Topaz II
terryhendicott21-Topaz IIAnswer
21-Topaz II
April 3, 2019

Hi,

 

Have included solving for the root of an equation for you.

Cheers

Terry

J
jst1251-VisitorAuthor
1-Visitor
April 3, 2019

Yes, the "root" approach is a much better option.  I hadn't used this before.  Thank you for sending the example.  It's exactly what I'm looking for.

W
Werner_E25-Diamond I
25-Diamond I
April 3, 2019

The solve block works exactly the way you had set it up but you can't simply use v1 etc. in your constraint because these are already vectors with h=1 and not dependent on h anymore.

You have to define v1 and v2 as functions dependent on h (I prefer to do this outside of the solve block)

B1.png

If you want to know the h for exactly 60 degree you may use the symbolic solve

B.png

and of course you could also use the root command

B3.png

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