Regarding the following sum and integration:
I don't understand the difference between t and 𝛕.
When nΔ𝛕 goes to zero the text says it becomes 𝛕. But why not t. Aren't an arbitrary point t and 𝛕 the same? I don't have such confusion with an integral such as f(x) = integral 3x dx or here.
But the equation in my question has both t and 𝛕 makes me very confused.
I'm missing something fundamental here but stuck with seeing the difference. How can we grasp the difference?