the very correct lebnitz theorem is as follows:-
i m using {"} for integral
d/dx [ {"}A(x)B(x) f(x,t)dt ] = [ {"}A(x)B(x) d'/d'x { f(x,t) dt } ] + dB/dx f(x,B) - dA/dx f(x,A)
here d'/d'x denotes partial differentiation wrt variable 't'
A(x) n B(x) denote functions of 'x'
IF UR GIVEN FUNCTION IS JUST IN ONE VARIABLE THEN THE TERM WITH PARTIAL DIFFERENTIATION BECOMES ZERO ...........................
AND THE RESULT IS WHAT GIVEN BY BIGGHE
************* SOMETIMES IT IS IMMPOSSIBLE TO INTEGRATE A GIVEN FUNCTION WITH THE GIVEN VARIABLE. IN THAT CASE USING THIS METHOD BECOMES EXTREMELY USEFUL AND NECESSARY i.e. first differentiate wrt one variable and integrate wrt other******************************** and then use standard integration ! ! ! ! !