Integral of a deriative. I've been learning the fundamental theore

hvacwk

hvacwk

Answered question

2021-12-21

Integral of a deriative.
I've been learning the fundamental theorem of calculus. So, I can intuitively grasp that the derivative of the integral of a given function brings you back to that function. Is this also the case with the integral of the derivative? And if so, can you please give a intuition for why this is true? Tha
in advance

Answer & Explanation

alkaholikd9

alkaholikd9

Beginner2021-12-22Added 37 answers

Since axf(t)dt=f(x)f(a) (1)
the short answer is that the integral of the derivative is the original function, up to a constant.
Of course, (1) isn't true without restrictions. But if f′ is continuous, then, yes, (1) holds.
Wendy Boykin

Wendy Boykin

Beginner2021-12-23Added 35 answers

The derivative and integral are almost inverse functions, so in turn, you are almost correct. For simple polynomials, one multiplies by the power and then removes 1 from the power, and the other adds 1 to the power and divide by the new power.
For more complex functions, you can consider it visually, or even compare it to physics. If you have a line (velocity), the gradient is the acceleration. If you derive this line to get the gradient, you know have the acceleration function. Now, if you have a flat line with no gradient (acceleration), and you integrate it, you will be left with a line with gradient for the velocity function.
This is because acceleration represents rate of change of distance relative to time, just like how gradient represents rate of change of y relative to x.
The only main difference is that integrating leaves you with an unknown constant C. You may notice that if you differentiate f(x)=2x2+3x+6, you're left with f(x)=4x+3, and the 6 has absolutely no effect on the final answer. This is because, no matter where the line/curve is located in the y-axis, the gradient for the x co-ordinate remains the same. You require a co-ordinate from the original function in order to calculate C.
nick1337

nick1337

Expert2021-12-28Added 777 answers

The integral of the derivative isn't always equal to the original function.
example : let f be a function as
f(x)=2x+2
so we have f(x)=2
If you integrate f', you'll end up with F(x)=2x+c
with c a real constant. So you'll have your initial function only if c=2

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