- #1
Taturana
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Greetings,
We know that the two operations (integration and differentiation) are inverse. I mean, if you integrate a function and differentiate the result of the first operation you go back to the first function. But I'm trying to understand WHY. Of course there are a lot of mathematical proofs for this, but I want to understand it intuitively, so I'm trying to understand it geometrically.
I had some progress with the following thought. But it doesn't prove my main question.
Consider the following:
http://img87.imageshack.us/img87/6942/integ.jpg
Uploaded with ImageShack.us
I have a random function at the left. I want to calculate the area under its graph from, say, x = 0 to x = 2, so I need to integrate. Geometrically I can divide the area under the graph into small columns (like the green one). Now, in order to calculate the total area under the graph I need to calculate all these columns areas and sum them.
The columns are going to be infinitely small, so if I zoom I will have something like a triangle in the top of the column and a big rectangle from the bottom of the triangle to the x axis. Now to calculate the area of this column, you calculate the area of the rectangle, the area of the triangle and sum them.
Here the differentiation comes in. In order to calculate the area of the triangle, I need to have the value of it's height. And the height of the triangle can be calculated using the tangent of angle theta (the derivative of the function at that x point). Now you do math, take the limits etc etc.
Okay, I already proved that the integration and the differentiation have an intrinsic relation: when I'm integrating (i.e. calculating the area under the curve) I'm constantly getting the derivative at every x's axis point inside the area.
But it doesn't prove that the derivative is the inverse operation of the integration (the antidifferentiation I mean).
Does anyone have any idea of how to prove that (geometrically)?
Thank you for the help.
We know that the two operations (integration and differentiation) are inverse. I mean, if you integrate a function and differentiate the result of the first operation you go back to the first function. But I'm trying to understand WHY. Of course there are a lot of mathematical proofs for this, but I want to understand it intuitively, so I'm trying to understand it geometrically.
I had some progress with the following thought. But it doesn't prove my main question.
Consider the following:
http://img87.imageshack.us/img87/6942/integ.jpg
Uploaded with ImageShack.us
I have a random function at the left. I want to calculate the area under its graph from, say, x = 0 to x = 2, so I need to integrate. Geometrically I can divide the area under the graph into small columns (like the green one). Now, in order to calculate the total area under the graph I need to calculate all these columns areas and sum them.
The columns are going to be infinitely small, so if I zoom I will have something like a triangle in the top of the column and a big rectangle from the bottom of the triangle to the x axis. Now to calculate the area of this column, you calculate the area of the rectangle, the area of the triangle and sum them.
Here the differentiation comes in. In order to calculate the area of the triangle, I need to have the value of it's height. And the height of the triangle can be calculated using the tangent of angle theta (the derivative of the function at that x point). Now you do math, take the limits etc etc.
Okay, I already proved that the integration and the differentiation have an intrinsic relation: when I'm integrating (i.e. calculating the area under the curve) I'm constantly getting the derivative at every x's axis point inside the area.
But it doesn't prove that the derivative is the inverse operation of the integration (the antidifferentiation I mean).
Does anyone have any idea of how to prove that (geometrically)?
Thank you for the help.
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