Using a solve block with a vector equation

[jst125]

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!

[terryhendicott]

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.

Then plot the function foo.

[ValeryOchkov]

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

[terryhendicott · Accepted solution]

Hi,

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

Cheers

Terry

[jst125]

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.

[Werner_E]

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)

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

and of course you could also use the root command