How Do We Solve the Definite Integral of log(sin(x))*log(cos(x)) from 0 to pi/2?

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AnhIn summary, to find the definite integral Int[ log(sin(x))*log(cos(x)) ,{x,0,pi/2} ] , you can express cos/sin in terms of an infinite product, split up the logs, and then continue with the solution. This method was also used by Wolstenholme in his solution to a similar problem.
  • #1
mathslover
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How should we proceed to find the definite integral


Int[ log(sin(x))*log(cos(x)) ,{x,0,pi/2} ] ?






mathslover
 
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  • #2
I can't remember the source of even the exact answer :( But I've seen integrals of that form done in some papers by Ramanujan where he expressed the answer in terms of the zeta function and something else, so it's not exactly an elementary integral.

This isn't how he did it, and I'm not sure if it will help, but you could express cos/sin in terms of an infinite product, split up the logs ( log [ab]= log [a] + log ) and then continue?
 
  • #3
Leafing through "Treatise on Integral Calculus Vol. 2 --Joseph Edwards (1922)",I found
Wolstenholme had solved the above problem nicely as follow:

-Ng
 

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1. What is a difficult integral?

A difficult integral is a type of mathematical problem that involves finding the area under a curve (or the definite integral) using complex equations and techniques. These integrals often require advanced knowledge of calculus and special methods to solve.

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