What is an antiderivative and can 1 function have more than one antiderivatives? I want to know wha

Brunton39

Brunton39

Answered question

2022-06-07

What is an antiderivative and can 1 function have more than one antiderivatives?
I want to know what the definition of an antiderivative is really. I know that the antiderivative of a function between 2 limits will give you the area under the graph between these limits. Take the function y = 1 / ( 2 x ). The integral will be ( 1 / 2 ) ln | x | or it can also be ( 1 / 2 ) ln ( 2 | x | ) which is equal to 0.5 ln ( 2 ) 0.5 ln | x | . So as you can see they differ only by a constant. So when you plug in two limits you will get the same value. But i am wondering what an antiderivative represents exactly and how can it be possible as you saw to have a function with 2 antiderivatives. And by the way, can an antiderivative be represented by a graphical method?

Answer & Explanation

lisicw2

lisicw2

Beginner2022-06-08Added 11 answers

Step 1
If you understand a derivative, you will understand that the derivative of a constant is 0.
You will also know that the derivative of f ( x ) + g ( x ) equals the derivative of f(x) plus the derivative of g(x), for appropriate conditions on f and g.
That means that if c is a constant, the derivative of f ( x ) + c is the same as the derivative of f(x).
So, suppose F(x) is the derivative of f(x).
That is, f(x) is the antiderivative of F(x).
Then F(x) is also the derivative of f ( x ) + c, whatever c is.
And in this context, c can be any real number.
That means there are as many different antiderivatives of F(x) as there are real numbers -- an uncountable infinity of them.
It can also be shown (but it needs a bit more advanced thinking) that if f(x) and g(x) are both antiderivatives of F(x), then g(x) is always going to be f ( x ) + c, where c is a constant.
That is, of all the antiderivatives of a given function, they are all the same except for being different by a constant.
Step 2
As for a graphical method, the antiderivative of f is the function whose gradient is f. You can get an approximation to it by picking a point in the plane (any point), say at x = x 0 , and calculate f ( x 0 ). Then you draw a short arrow with that gradient. The end of that arrow is at x = x 1 . You calculate f ( x 1 ) and draw another short arrow with the gradient equal to f ( x 1 ), that is, the gradient at that point. And so on, drawing a line made up of short arrows. As the length of the arrow tends to 0, the line represents the curve that is an antiderivative of f.
Taniyah Estrada

Taniyah Estrada

Beginner2022-06-09Added 5 answers

Explanation:
An antiderivative is just a function whose derivative is the function you're after. So in your example, 0.5 ln | x | and 0.5 ln | 2 x | are both antiderivatives of 1 2 x . A function actually has infinitely many antiderivatives, because the + C you get can be any real number. The reason there are so many is that taking a derivative eliminates any constant terms, so adding a constant to an antiderivative doesn't change the fact that taking its derivative gets you back the original function.

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