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Hi, i have a math question. Can i find the roots of inequalities in C# - is there any algorithm. For example the equation is
x^4 + 3*x^2 + 8 > 0 or sin(2*x) + cos(3*x) < 1
...
How can i find with a program the roots of these inequalities?
I need to know this because i am writing a program which draws math graphs. It can draw inequalities (for example sin(2*x) < cos(x) ) and mark the intervals at which inequality has roots (where sine is smaller than cosine from the example). The hard part is that i can't find the points where the inequalities intersect - i can't find the bounds of the intervals where the solutions are.
Still learning...
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Hi,
you can solve a small fraction of all possible equations analytically; e.g. your first
example is a quadratic equation, where x^2 is the unknown. Since the discriminant is
negative, it will have four complex solutions, no real ones.
Your second example can be transformed into a pair of equations in s and c, where
s=sin(x) and c=cos(x), the second equation being s*s + c*c = 1
For plotting purposes you don't really need an analytic solution; you can just somehow
define the range that interests you, and calculate the function for several values inside
that range.
And you can always try and solve an equation of the form f(x)=0 by an iterative
approach, see e.g. Newton-Raphson algorithm.
Luc Pattyn [Forum Guidelines] [My Articles]
This month's tips:
- before you ask a question here, search CodeProject, then Google;
- the quality and detail of your question reflects on the effectiveness of the help you are likely to get;
- use PRE tags to preserve formatting when showing multi-line code snippets.
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you could try using the api for something like matlab, but I suspect MatLab is very expensive, I've only every used a copy in a university computing lab.
Otherwise You'll need to write code to solve general cases of each equation or an algebra module to rearrange the equations into a general case.
As Luc has already said something like Newton Raphson might be a good idea but you need to have a rough idea of where the roots are inorder to find all of them
HTH
Russell
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Clicking on the Export button will show a window in which to set the name of the exporting file. The Field delimiter will also need to be specified (the column separator character) and you will also be able to specify whether First row contains field names. Finally, you’ll be able to select the fields to be exported and, after clicking on the Next button, exporting process will start.
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Smells like an assignment. Anyway, Google is your friend as well as codeproject.
Giorgi Dalakishvili
#region signature
my articles
#endregion
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Hi, my whole question is in the subject... In regular desktop framework i can just construct my own cursor. but when working with CF i noticed that it's impossible, because no constructor is exposed. Nonetheless there are programs which can do this. How? I have no clue. Perhaps you can help me thanks guys
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Hi All,
I am new with VS 2008 and WPF application. so i am making a WPF Application but now i have to add "tab bar" like office 2007 instead of menues.
can anyone please tell me how to add tab bar on main window of WPF application.
Thanks
Bankey
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Hi,
Can anyone of you, tell me how to call c++ functions from c# program?
I have a C++ dll, in which i have some functions, now i want to call them from my c# code. Please tell me how can i do this. If possible provide me sample code n all.
Thank you in advance
Bye,
sree
sree
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You need to write a wrapper for C++ dll in C#. Use DllImport[^] attribute.
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Hi Navaneeth,
I have tried it, but i ended with an exception " unable to find an entry point named function-name in dll".Can u provide some more detailed information regarding this.
sree
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The C++ function name will be mangled, see here[^].
Alternatively you could wrap the DLL in a inprocess COM object and use COM Interop to use it.
If you want to avoid issues with the Name Mangling (which is non-standard accross compilers) then you need to write a C DLL, rather than a C one.
regards,
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Hey Guys,
I just got the scariest Exception I've ever seen!
It reads... AccessViolationException Was Unhanded, Attempted To Read Or Write Protected Memory. This is often an indication that other memory is corrupt.
In Visual Studio It points out Application.Run(new frmMain()); As the culprit
I have no idea why this happens, it seems random because i call only one method and it works most of the time. Even when i do get the Exception the program got around to logging data in my database (thhis is the 2nd last step of the process I'm coding) So im thinking it might be where i call These methods...
cmd.Dispose();
newSqlConn.Close();
newSqlConn.Dispose();
But i might be wrong, i still need a way to replicate the damn error so that i can step though the code and see exactly where it breaks.
So my question is this, have any of you ever come across this error? Why does it happen and where do u think i should start looking to fix it?
thanx
Harvey Saayman - South Africa
Junior Developer
.Net, C#, SQL
think BIG and kick ASS
you.suck = (you.passion != Programming)
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I've come across it when painting to picture boxes containing a bitmap. I was attempting to write colour to a segment of the box but I forgot to convert the bmp back from monochrome after some processing I did, also attempting to point at a segment outside of the bounds of the bmp caused this (but that was more obvious to spot). Other than that, I haven't come across it before.
He who makes a beast out of himself gets rid of the pain of being a man
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i do no painting in this particular program...
im getting data from an external device and writing it to my database, the weird thing is that it works most of the time. i wish it gave me more info on whats going wrong...
Harvey Saayman - South Africa
Junior Developer
.Net, C#, SQL
think BIG and kick ASS
you.suck = (you.passion != Programming)
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Unfortunately I can't help then, that's the extent of my experience with this exception, hopefully someone else will be along shortly to help you out
He who makes a beast out of himself gets rid of the pain of being a man
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i hope so too,
thanx tho
Harvey Saayman - South Africa
Junior Developer
.Net, C#, SQL
think BIG and kick ASS
you.suck = (you.passion != Programming)
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Exceptions often get thrown in Application.Run. I *think* its just the exception bubbling up to the top level handler. You could try putting methods further up the call stack in exception blocks and make sure you've got first chance exception throwing switched on in the debugger to narrow it down a bit.
You must be using some sort of interop or 3rd party component no?
Regards,
Rob Philpott.
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i am, im using an SDK provided by the manufacturer of the external device im getting data from. its a fingerprint scanner by the way.
without it i cant communicate with the device...
Harvey Saayman - South Africa
Junior Developer
.Net, C#, SQL
think BIG and kick ASS
you.suck = (you.passion != Programming)
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Ah, what form does this SDK take and how do you call it?
Regards,
Rob Philpott.
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its a class, first i add a reference to the project, then a using zkemkeeper;, then i make an instance of the class and the call methods from that instance in this fassion.
private void button1_Click(object sender, EventArgs e)
{
CZKEMClass zkSDK = new CZKEMClass();
if (zkSDK.Connect_Com(1, 1, 115200))
{
if (zkSDK.ReadAllGLogData(1))
{
int badgeNo = 0;
int verifyMode = 0;
int inOutMode = 0;
string dateTime = "";
while (zkSDK.GetGeneralLogDataStr(1, ref badgeNo, ref verifyMode, ref inOutMode, ref dateTime))
{
MessageBox.Show(badgeNo + "\r\n" + verifyMode + "\r\n" +inOutMode + "\r\n" + dateTime);
}
}
zkSDK.Disconnect();
}
}
Harvey Saayman - South Africa
Junior Developer
.Net, C#, SQL
think BIG and kick ASS
you.suck = (you.passion != Programming)
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Hmm. Is that a normal .NET class or a COM wrapper?
If you've defined some COM/unmanaged interop and you haven't got it quite right things like this can happen. Memory can get corrupted and your application can leak. Usually horrid things like calling conventions and the like.
If you're just using this 3rd party stuff without defining any interop yourself I think you can probably assume that is a problem with that and not you. Managed code just can't raise exceptions like the one you're getting.
Regards,
Rob Philpott.
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that is literaly all i do hey...
the reference i add is a dll and while hovering over it it says "active x control for zk embedded fingerprint T7A system"
Harvey Saayman - South Africa
Junior Developer
.Net, C#, SQL
think BIG and kick ASS
you.suck = (you.passion != Programming)
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Harvey,
When using classes from interop assemblies (like CSKEMClass) you, as a developer, are responsible for cleaning up any resources you use in your program. Not doing so might cause AccessViolationExceptions and will leak memory because the memory isn't freeed properly.
Try using the following pattern:
CZKEMClass zkSDK = new CZKEMClass();<br />
zkSDK.Disconnect();
<br />
Mashal.ReleaseComObject(zkSDK);
Hope it helps.
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Hey there
thanx for the the suggestion, which namespace mast i reference to get Marshal? All i see in intellisence is MarshalByRefObj
thanx
Harvey Saayman - South Africa
Junior Developer
.Net, C#, SQL
think BIG and kick ASS
you.suck = (you.passion != Programming)
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