What is Second derivative: Definition and 178 Discussions

In calculus, the second derivative, or the second order derivative, of a function f is the derivative of the derivative of f. Roughly speaking, the second derivative measures how the rate of change of a quantity is itself changing; for example, the second derivative of the position of an object with respect to time is the instantaneous acceleration of the object, or the rate at which the velocity of the object is changing with respect to time. In Leibniz notation:





a

=



d

v



d
t



=




d

2



x



d

t

2





,


{\displaystyle \mathbf {a} ={\frac {d\mathbf {v} }{dt}}={\frac {d^{2}{\boldsymbol {x}}}{dt^{2}}},}
where a is acceleration, v is velocity, t is time, x is position, and d is the instantaneous "delta" or change. The last expression








d

2



x



d

t

2








{\displaystyle {\tfrac {d^{2}{\boldsymbol {x}}}{dt^{2}}}}
is the second derivative of position (x) with respect to time.
On the graph of a function, the second derivative corresponds to the curvature or concavity of the graph. The graph of a function with a positive second derivative is upwardly concave, while the graph of a function with a negative second derivative curves in the opposite way.

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  1. D

    Finding first and second derivative

    how would I find the first and second derivative of (x^3/3) - 2x^2 + 3x +8 thanks
  2. A

    How to get the second derivative of this function ?

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  3. L

    Second Derivative of 3sec\sqrt{x}

    Homework Statement Find the second derivative of 3sec\sqrt{x} Homework Equations derivative of sec u = secu(tanu)*u' product rule- (F*G)'=f'*g+g'*f quotient rule- (F/G)'=(f'*g-f*g')/g^2 The Attempt at a Solution So i did the first derivative of it, getting...
  4. D

    Second derivative of effective potential

    Determine the value of r in terms of l, k, and m for which the following function has a minimum. V(r) = -(k/r) + (l^2/(2mr^2)) where l, k, and m are positive constants. Prove that this is a minimum by showing that the second derivative of V(r) at the minimum is positive. I have no...
  5. O

    F''(x) Second Derivative problem

    Homework Statement find f''(x) <-- second derivative f(x) = 3e^-x2 <-- that 2 is x squared Homework Equations The Attempt at a Solution my attempt was 6x^2 e^x2
  6. A

    Understanding Parametric Second Derivative through Polynomial Division

    I'm having trouble seeing how an example comes out because the "worked example" skips about 5 steps and I can't get from point a to b. It starts as: \frac{\frac{d}{dt}(\frac{3t^{2}-3}{3t^{2}-6t})}{3t^2-6t} and is meant to end up as: \frac{-2(t^{2}-t+1)}{3t^{3}(t-2)^{3}} I end up with a...
  7. A

    How can there be a function with a second derivative greater than zero

    Homework Statement yet is approaching negative infiniti? We were discussing a question that went "suppose f double prime (x)>0 and x ranges from negative infiniti to infiniti, and f(a)=0. Prove or disprove that f(x) is bounded below." The man said that e^-x - x had a second derivative...
  8. J

    Riemann curvature tensor as second derivative of the metric

    It is a standard fact that at any point p in a Riemannian space one can find coordinates such that \left.g_{\mu\nu}\right|_p = \eta_{\mu\nu} and \left.\partial_\lambda g_{\mu\nu}\right|_p. Consider the Taylor expansion of g_{\mu\nu} about p in these coordinates: g_{\mu\nu} = \eta_{\mu\nu}...
  9. E

    Second derivative of e^x minus e^x

    Homework Statement Show that y(t) = e^t is a solution of y'' - y = 0, Homework Equations integral of e^x dx = e^x +c derivative of e^x = e^x The Attempt at a Solution set m = d(e^t)/dt, which also = e^t then dm = e^t then d(m)/dt = e^t if y(t) = e^t is a solution integrate...
  10. E

    What is the Second Derivative of xtanx?

    Homework Statement Given y=xtanx, find y'' (second derivative) Homework Equations Uh... I'm not even sure if I'm using the right one... d/dx(tanx) = sec^2x The Attempt at a Solution y=xtanx y'= (x)(sec^2(x)) + (tanx)(1) y'= xsec^2(x) + tanx y'' = [(x)(2sec^3(x)) +...
  11. D

    The second derivative question

    Homework Statement Given (d^2)x/ (dt^2) = 2 for all t>= 0 and dx/dt= -5 and x= 4 when t= 0 find t when a) dx/ dy= 0 b) x= 0 2. The attempt at a solution a) Given (d^2)x/ (dt^2) = 2, then dx/dt= 2x + c = -5 given dx/ dt= 0 then 2x + c= 0 c= -2.5 using 2x + c= 0 and 2x + c =...
  12. D

    Easy second derivative question

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  13. N

    Finding the second derivative of multvariable function

    Hello I am trying to figure out the second derivative of \frac{\partial^2 z}{\partial x^2} and \frac{\partial^2 z}{\partial t^2} z(u) and u=x-vt i found the first derivate of \frac{\partial z}{\partial x} to be \frac{\partial z}{\partial x}= \frac{\partial z}{\partial u} *...
  14. B

    Using the Second Derivative Test

    Homework Statement Find all relative extrema using the second derivative test for H(x) = x * lnx Homework Equations The Attempt at a Solution H'(x) = (1 * ln x) + (x * 1/x) = lnx + 1 H''(x) = 1/x + 0 Is H''(x) right? Then I am having trouble finding the relative extrema from...
  15. M

    Taking the Second Derivative w/ the Quotient Rule: What if Numerator = 0?

    Just wondering how you take the second derivative when using the quotient rule. After using the quotient rule to get my first derivative, I tried again and the numerator ended up as 0.
  16. S

    Geometric Interpretation of Second Derivative

    I would like someone to tell me what is the geometric interpretation of the second derivative at a fixed point, or in an interval?? thx
  17. B

    Proving the Second Derivative Using L'Hopital's Rule

    Homework Statement Show that lim(h-->0) [f(x+h)-2f(x) + f(x-h)]/h^2 is equal to f''(x) for any given value of x where the second derivative exists. I'm supposed to use L'Hopitals rule for this problem. I did and got [f(x+h)-f(x-h)]/2h Now I am stuck. I thought about adding and...
  18. R

    Determine the minimum using the second derivative

    I was wondering if someone could show me where to go next in this problem. I need to determine the minimum length, width and height that a 1 cubic foot box can have. This box does not have a top. I know that I need to minimize the area, but I'm not sure if I'm going about this correctly. So...
  19. N

    Implicit Differentiation - Second Derivative

    Were assigned questions regarding implicit differentiation and the second derivative but did not receive a formal lesson so I need some explanations. Example: Find the second derivative x^3 + y^3 = 1 I found this solution on the internet and the answer matches the one in the textbook...
  20. R

    Why is Concavity and Inflection Points Important for Calculus AB?

    I am Calculus AB student. I know how to find first derivative, second derivative, prove points of inflecition, find concavity...but as I just finnished the last section of chapter 4 and chapter 5 is Integrals, I still have one question that remains unanswered: Why is it important to find...
  21. Orion1

    Second Derivative Theorems

    I am posting my theorems for peer review, anyone interested in posting some proofs using some simple functions? Can these theorems be reduced into simpler equations? Orion1 Second Derivative Theorems: \frac{d^2}{dx^2} (x) = 0 \frac{d^2}{dx^2} (x^2) = 2 \frac{d^n}{dx^n} (x^n) = n...
  22. S

    Second Derivative Doesn't Work

    Starting with y^2-xy=2, then y'=y/(2y-x) y''=(2y-x)y'-y(2y'-1)/(2y-x)^2 substitute y' in: y''=(2y-x)(y/2y-x) - y(2(y/2y-x)-1) the (2y-x) cancels: y''=(y) - y(2y/2y-x)-1) distribute: y'' = y - (2y^2)/(2y-x)-y Somewhere I need y^2-xy so I can replace it with the original 2, but...
  23. SpaceTiger

    Diagonalizing a 3x3 second derivative matrix

    I've been working on this problem lately where I've been looking at the second derivatives of 2D and 3D density fields. Now, the second derivatives of the field can be represented in a matrix, which can be thought of as an N-dimensional ellipse with the principal axes aligned along some angle...
  24. J

    Problem on finding second derivative.

    I have a problem on finding the second derivative for this function: \frac {x}{x^2-4} For the first derivative, I got: \frac {-x^2-4}{(x^2-4)^2} Now here is where I am stuck! So far for the second derivative, I got this (Please check!): \frac...
  25. J

    Problem on finding the second derivative.

    I have a problem on finding the second derivative for this function: \frac {x}{x^2-4} For the first derivative, I got: \frac {-x^2-4}{(x^2-4)^2} Now here is where I am stuck! So far for the second derivative, I got this (Please check!): \frac...
  26. E

    Calculus: Second derivative

    Find the second derivative by implicit differentiation: x^3 + y^3 = 6xy Wow, a lengthy question when you have to show all your work. Anyway, for the first derivative I got: \frac {2y-x^2}{y^2-2x} How would one start to calculate the second derivative? I tried the Quotient Rule...
  27. E

    MATLAB Matlab Second Derivative Ploting Problem

    Hello, this is my first post in this site, so here goes: Im working on a Matlab program. I have to calculate the second derivative of a given equation. The problem is that plotting the derivative is necessary, and that's where I'm stuck. Here's what I've got so far: % Evaluar f(x) y...
  28. I

    L'Hopital / Second Derivative

    Any help you can give me would be appreciated! The teacher wrote the solution to the problem on the board without giving much explanation of how he got there, and now he wants the third derivative, so I was wondering if you could help answer how he got the second. g(x) [the lim. as x goes...
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