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diverger1-Visitor
1-Visitor
May 23, 2013
Solved

How to solve an equation with multiple solutions?

  • May 23, 2013
  • 2 replies
  • 5857 views

I've a problem to solve such equations, one unknown variable, but infinite solutions, it seems mathcad only return the first one, anyone can confirm this ? And how to handle these equations in MatchCAD?

Thanks.

Best answer by ptc-4735478

to find the first 5 - 10 roots first, you just have to search for the root within certain interval of x, change this interval and u find a new root. you pretty much almost have 1 solution for every half a period and less. look up root function in the mathcad help file. You can set the interval for which you are searching the solution.

and when t is large enough, the exponential function approach 0. thats why valery said the solution is just cos = 0 after couples of solution.

2 replies

V
24-Ruby IV
ValeryOchkov24-Ruby IV
24-Ruby IV
May 23, 2013

I think you can use a numerical math for first 5-10 roots and than cos(t)=0

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diverger1-VisitorAuthor
1-Visitor
May 23, 2013

Any details? I'm new to MathCAD, can you give me one example? 5~10 roots are enough for me, thanks.

P
ptc-47354781-VisitorAnswer
1-Visitor
May 23, 2013

to find the first 5 - 10 roots first, you just have to search for the root within certain interval of x, change this interval and u find a new root. you pretty much almost have 1 solution for every half a period and less. look up root function in the mathcad help file. You can set the interval for which you are searching the solution.

and when t is large enough, the exponential function approach 0. thats why valery said the solution is just cos = 0 after couples of solution.

D
diverger1-VisitorAuthor
1-Visitor
May 23, 2013

Thanks, the problem solved.

V
24-Ruby IV
ValeryOchkov24-Ruby IV
24-Ruby IV
May 23, 2013

You welcome:

roots.png

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    diverger1-VisitorAuthor
    1-Visitor
    May 23, 2013

    The root function takes the form root(f(var), var, [a, b]). It returns the value of

    var to make the function f equal to zero. The real numbers a and b are optional.

    If they are specified (bracketed), root finds var on this interval. The values of a

    and b must meet these requirements: a < b and f(a) and f(b) must be of opposite

    signs.

    It seems i must plot the two curves, then manually set the interval, or it won't give correct answer. Right ?

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