- #1
member 428835
Hi PF!
Can anyone help me with showing the following: $$\frac{\partial}{\partial x} \int_{f(x)}^{g(x)} L(x,y)dy = \int_{f(x)}^{g(x)} \frac{\partial L}{\partial x} dy + \frac{\partial g}{\partial x} L(g,y) - \frac{\partial f}{\partial x} L(f,y)$$
I understand this as the fundamental theorem if ##\frac{\partial L}{\partial x} = 0## but how do I deal with this if it is not equal to zero? i was thinking about trying to say let ##F(x,f,g) = \int_{f(x)}^{g(x)} L(x,y)dy## and use chain rule but I'm not sure how to deal with the boundary terms.
Thanks!
Can anyone help me with showing the following: $$\frac{\partial}{\partial x} \int_{f(x)}^{g(x)} L(x,y)dy = \int_{f(x)}^{g(x)} \frac{\partial L}{\partial x} dy + \frac{\partial g}{\partial x} L(g,y) - \frac{\partial f}{\partial x} L(f,y)$$
I understand this as the fundamental theorem if ##\frac{\partial L}{\partial x} = 0## but how do I deal with this if it is not equal to zero? i was thinking about trying to say let ##F(x,f,g) = \int_{f(x)}^{g(x)} L(x,y)dy## and use chain rule but I'm not sure how to deal with the boundary terms.
Thanks!