How do I find these ANTI-DERIVATIVES?

Given a function f(x) we can use old derivative rules to help find the antiderivative up to an additive constant. Find the antiderivative of the given functions:

1. f(x) = 3x^2
Is the anti-derivative x^3 + c?

2. m(x) = (-2/y^3)
Is the anti-derivative (1/2) y^-4 + c?

I’m not really sure anymore how to find the rest of these anti-derivatives.
3. g(x) = x ^ π

4. h(x) = cos x

5. p(x) = 1/ (x^2 + 1)

Thanks for the help!

✅ Answers

? Best Answer

  • 1. f(x) = 3x^2

    We get …

    3 (1/3) x^3 + c = x^3 + c

    2. m(x) = (-2/y^3)

    We re-write it as …

    -2 y^-3

    and get …

    -2 (-1/2) y^-2 + c

    which becomes …

    y^-2 + c

    which becomes …

    1 / y^2 + c

    3. g(x) = x ^ π

    Treat π as a constant (such as ‘2’) and we get …

    1/(π+1) x^(π+1) + c

    4. h(x) = cos x

    The derivative of Sin(x) is Cos(x) hence we get …

    sin(x) + c

    5. p(x) = 1/ (x^2 + 1)

    The derivative of arctan(x) is 1/(x^2 + 1) hence we get …

    arctan(x) + c

    Arctan(x) means 1/tan(x)

  • 1. f(x) = 3x^2
    Is the anti-derivative x^3 + c?
    yes
    2. m(x) = (-2/y^3)
    Is the anti-derivative (1/2) y^-4 + c?
    you have a confusion of x’s and y’s…

    -2y^-3 would become y^-2

    I’m not really sure anymore how to find the rest of these anti-derivatives.
    3. g(x) = x ^ π

    Just like x^any number… don’t let it throw you that it is not an integer.

    G(x) = (1/(π+1))x ^ (π+1) +c

    4. h(x) = cos x
    H(x) = sin x +c .. I don’t have the space here to derive this one… the derivative of sin x = cos x the derivative of cos x = -sin x

    5. p(x) = 1/ (x^2 + 1)

    P(x) = tan^-1 x +c

    And this one is even more difficult to explain here…

    you could get tricky with it, too…

    1/ (x^2 + 1) = 1/(x+i)(x-i) = 1/2i (1/(x+i) – 1/(x-i))
    P = 1/2 i (ln(x+i) – ln(x-i))+c = 1/2 i ln(x+i)/(x-i) +c

    but inverse tangent is the safer way to go…

  • 1. correct
    2. Why that is brilliant! -4 = -3 + 1 ….I wish I had your skills in addition
    3. 3.1415926… + 1 = 4.1415926… what is your problem?
    4. oh, I see… either you don’t know the differential for sin(x) or you have ADD or you are just lazy.
    5. (x²+1)⁻¹ … apparently you don’t know the differentials for the inverse trig functions either…

  • 3) = x^ ( pi + 1)
    …… —————- + c …………………………….. Power rule
    ……… pi + 1

    4) = -sin x + c

    5) = arc tan x + c

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