can sumone xplain to me how the 3rd step is reached from the 2nd?
follow the link: http://upload.wikimedia.org/math/f/d/2/fd207a836f1b8e151595257c618b6fa9.png

Question

anonymous · Answer

$$\int\limits_{a}^{b} \frac {dL}{dy}dy =L(b)-L(a)$$

anonymous · Answer

noe here u did the integration with respect to y and the limits were g2(x) and g1(x) so in place of y they put that..

anonymous · Answer

well thats okay n all but there is partial differentiation of L w.r.t y which is certainly different from the regular dy

anonymous · Answer

yes... i knew that...i think u have the problem that i wrote dy instead of del y...

anonymous · Answer

see del y helps u to deal with only y keeping x constant...

anonymous · Answer

so L being a function of x and y u consider x as constant...for example $$\int\limits_{a}^{b}\frac1{x+y}\delta y =\ln|x+y||_{a}^{b}$$

anonymous · Answer

okay, i think i get it.

anonymous · Answer

hello....any problem??

anonymous · Answer

okay just for clarification, can you show me,
del L(x,y) dy = L dy
del y

anonymous · Answer

what do mean by del L(x,y) dy =Ldy???