how to solve these equations
Hi all,
I want to solve the two equations u*tan(u)=w and u^2 + w^2=V^2, where V is a known constant, and u and w are the two unknowns to be determined. Please can someone suggest me how to write a code and solve these equations in C or C++? I am not an expert, but have elementary working knowledge of C. Thanks vj 
Re: how to solve these equations
vj wrote: > Hi all, > > I want to solve the two equations > > u*tan(u)=w > and > u^2 + w^2=V^2, where V is a known constant, and u and w are the two > unknowns to be determined. Please can someone suggest me how to write a > code and solve these equations in C or C++? I am not an expert, but > have elementary working knowledge of C. You need algebra. If these are a system then it can easily be solved using math. If they are not a system the only way to "solve" such equations is to loop until you get to a certain point close to the answer. It doesn't look to me like that kind of problem though. Some equations are not solvable but you know when you get close to your answer and how to change the variable to get closer. I find this a lot in my job working on software that makes use of fluid mechanics in calculations. You can also solve them for input in one of the variables and output the value of the other. This is also a simple matter of using basic algebra to solve for a variable. 
Re: how to solve these equations
vj wrote:
> I want to solve the two equations > > u*tan(u)=w > and > u^2 + w^2=V^2, where V is a known constant, and u and w are the two > unknowns to be determined. Please can someone suggest me how to write > a code and solve these equations in C or C++? I am not an expert, but > have elementary working knowledge of C. You need to look up "NewtonRaphson method", most likely. It's not topical here. Try sci.math.* hierarchy. Since you have elementary working knowledge of C, you already know how "to write a code". Begin with "int main(" and proceed to write all the necessary code for the algorithm that you already have. If you don't have the algorithm, we can't help you. It's not a C++ language problem. V  Please remove capital 'A's when replying by email I do not respond to topposted replies, please don't ask 
Re: how to solve these equations
vj,
The first hit on google, if you search for "solving systems of equations" (no quotes). http://regentsprep.org/Regents/math/...picCode=syslin Doug vj wrote: > Hi all, > > I want to solve the two equations > > u*tan(u)=w > and > u^2 + w^2=V^2, where V is a known constant, and u and w are the two > unknowns to be determined. Please can someone suggest me how to write a > code and solve these equations in C or C++? I am not an expert, but > have elementary working knowledge of C. > > Thanks > > vj > 
Re: how to solve these equations
On Wed, 23 Aug 2006 08:34:37 0700, vj wrote:
> Hi all, > > I want to solve the two equations > > u*tan(u)=w > and > u^2 + w^2=V^2, where V is a known constant, and u and w are the two this looks like a trigonometrical problem. assume there is a triangle with the right angle sides u ans w and the opposite side V, eg, pythagorian triangle.. the first equation is tan(u)=w/u which is the normal definition of tan() but the angle in numbers must be equal to one of the sides. I presume the u in tan(u) is in radians not in degrees? thats all i can see for now.. > unknowns to be determined. Please can someone suggest me how to write a > code and solve these equations in C or C++? I am not an expert, but have > elementary working knowledge of C. > > Thanks > > vj 
Re: how to solve these equations
> You need algebra. > > If these are a system then it can easily be solved using math. > > If they are not a system the only way to "solve" such equations is to > loop until you get to a certain point close to the answer. It doesn't > look to me like that kind of problem though. Some equations are not > solvable but you know when you get close to your answer and how to > change the variable to get closer. I find this a lot in my job working > on software that makes use of fluid mechanics in calculations. > > You can also solve them for input in one of the variables and output > the value of the other. This is also a simple matter of using basic > algebra to solve for a variable. my instinct tells me the solution to this problem is to loop until you get close to an answer. basically a brute force solution 
Re: how to solve these equations
vj wrote:
> Hi all, > > I want to solve the two equations > > u*tan(u)=w > and > u^2 + w^2=V^2, where V is a known constant, and u and w are the two > unknowns to be determined. Please can someone suggest me how to write a > code and solve these equations in C or C++? I am not an expert, but > have elementary working knowledge of C. > > Thanks > > vj > Replace w in the second equation with its expression in terms of u. Use the trig identity 1 + tan^2 = sec^2 and apply a square root to make it even simpler. Then look up Newton's method. 
Re: how to solve these equations
On Wed, 23 Aug 2006 17:04:10 GMT, Mark P
<usenet@fall2005REMOVE.fastmailCAPS.fm> wrote: >vj wrote: >> Hi all, >> >> I want to solve the two equations >> >> u*tan(u)=w >> and >> u^2 + w^2=V^2, where V is a known constant, and u and w are the two >> unknowns to be determined. Please can someone suggest me how to write a >> code and solve these equations in C or C++? I am not an expert, but >> have elementary working knowledge of C. >> >> Thanks >> >> vj >> > >Replace w in the second equation with its expression in terms of u. Use >the trig identity 1 + tan^2 = sec^2 and apply a square root to make it >even simpler. Then look up Newton's method. This query has all the earmarks of a homework problem, in my opinion. Some help and guidance, like "look up Newton's method" might be appropriate. I am not sure just how much more explicit information would be. 
Re: how to solve these equations
Douglas Reed wrote:
> vj, Please don't toppost. Your replies belong following or interspersed with properly trimmed quotes. See the majority of other posts in the newsgroup, or the group FAQ list: <http://www.parashift.com/c++faqlite/howtopost.html> Brian (lots of 'em today) 
To solve equations of this type you need to to learn algebra for a quick lesson you can visit tutorvista.com

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