hey .. this mite be an incredibly stupid question.. but its been buggin me for a long long time.... lets say i need to integrate an expression from zero to a very large value( say 2 times greater than the earths radius)... so do i need to integrate it upto infinity or is it enough if i integrate it upto tat big value!!!! thanks ...
Not knowing exactly what you are integrating, it is a general rule that if you have a finite limit, then you should integrate to that limit. Integrating to infinity should only be generally done when one requires a "total sum" of the function, for example when calculating total field strengths in electro-magnetics, as opposed to calculating field strength between physical limits.