Sign in to follow this  
Followers 0
baltoche

Integral

6 posts in this topic

Dear All,

 

I'm trying to find a primitive of f(x)=cos(-Asin(x)) where A is a constant number.

I've tried Wolfram but unsuccessfully. An approximate function of this primitive would also be welcome.

 

Thanks for your help !

 

Kind Regards.

0

Share this post


Link to post
Share on other sites

  Wolfram did not work because the primitive of this function is not an "elementary function" (so cannot be written in terms of trig functions, exponentals, logs, etc.).

0

Share this post


Link to post
Share on other sites

I know the values between whom I need to integrate this function, but it does not solve my issue... Regarding numerical methods (calculating a rough surface for instance), I cannot do it since my final integral will be a function of A.

If the answer is not an elementary function, is there a way to approach it ?

 

Thanks in advance.

0

Share this post


Link to post
Share on other sites

Well  numerical integration will just give you a numerical area, and I suppose that you want a plot of the primitive?

 

If you differentiate your equation that will turn it into a differential equation.

You can then create the plots by one of several numerical methods starting from the (presumably known) boundary conditions.

 

Edit A thought occurred to me

 

When you wrote this

 

 

 

I'm trying to find a primitive of f(x)=cos(-Asin(x)) where A is a constant number.

 

Did you mean the formula is the derivative of the function?

 

That is did you mean f'(x)=cos(-Asin(x)) ?

 

In which case you already have a differential equation to work on.

Edited by studiot
0

Share this post


Link to post
Share on other sites

Hello Studiot,

 

Thanks for your kind contribution. Ideally, I'm after a function of A in order to plot it, knowing that I know between what values (O and Pi) I need to integrate this function. Actually, I asked for the primitive in order to calculate the integral, which is also a function of A, and this is the one I'd like to plot.

 

For your information, this primitive/integral is needed too solve Bessel's equation and function.

 

I'm sorry for the poor quality of my English.

 

Kind Regards.

0

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0