What is an integral?

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I’m in CalcII now and for the life of me cannot wrap my head around integrals. Now we are using things like u-Substitution methods and solving the areas between 2 curves. I can understand how the equations work, but not why because I still cannot picture what an integral is or why it’s important.

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Anonymous 0 Comments

It’s the inverse operation of a derivative.

F'(x) = f(x)

∫f(x)dx = F(x)

It’s the amount of area under a given curve.

If we take a curve and break the area underneath it into several rectangles, the height of a given rectangle is f(x), and the width of the rectangle is Δx

The area of one of those rectangles would be f(x) * Δx

Now, we need to add all of those rectangles together.

If we split the area into n rectangles, and we integrate from a to b, so our rectangle heights are f(a), f(a+Δx), f(a+2Δx),… until f(b). The width of all the rectangles is Δx.

Δx = (b-a)/n

Now we just add them all together. Σ (i=0->n) f(a+i Δx)Δx

When we take the limit as n->infinity, then it becomes an integral

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