Finding dx/dt & d^2x/dt^2 for x+e^x=t

  • Thread starter coverband
  • Start date
In summary, the equations and attempts at finding dx/dt and d^2x/dt^2 for the given problem are provided, with the correct solution for dx/dt and the incorrect solution for d^2x/dt^2 being discussed and corrected using the chain rule.
  • #1
coverband
171
1

Homework Statement



x+e^x=t. find dx/dt and d^2x/dt^2

Homework Equations





The Attempt at a Solution


dt/dx = 1 + e^x
Therefore dx/dt = (1+e^x)^-1 This is right.
d^2x/dt^2 = 0. This is wrong. Why?
 
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  • #2
coverband said:

Homework Statement



x+e^x=t. find dx/dt and d^2x/dt^2

Homework Equations


The Attempt at a Solution


dt/dx = 1 + e^x
Therefore dx/dt = (1+e^x)^-1 This is right.
d^2x/dt^2 = 0. This is wrong. Why?

Because x is a funtion of t, not constant. You need to use the chain rule. And it would also have been more in the spirit of the problem to differentiate the original equation implicitly instead of solving for t.
 
  • #3
yea, its not 0

how do you differentiate

(1+ex)-1 ??
 
  • #4
Well, given that x=x(t) (x being a function of t) you get [tex] -(1+e^x)^{-2}*e^x*\frac{dx}{dt} [/tex] And you've already calculated dx/dt.
 

1. What is the meaning of dx/dt and d^2x/dt^2?

dx/dt represents the first derivative of x with respect to time, also known as the instantaneous rate of change. d^2x/dt^2 represents the second derivative of x with respect to time, which is the rate of change of the rate of change or the acceleration.

2. How do you find dx/dt and d^2x/dt^2 for a given equation?

To find dx/dt and d^2x/dt^2 for an equation, you need to first differentiate the equation with respect to time using the rules of calculus. This will give you the first and second derivative expressions, which can then be simplified and solved for the given value of t.

3. What is the significance of finding dx/dt and d^2x/dt^2 for a given function?

Finding the derivatives of a function allows us to understand the behavior of the function over time. It helps us determine the rate of change and acceleration of the function at any given point, which can be useful in predicting future behavior and making decisions based on that.

4. Can dx/dt and d^2x/dt^2 be negative or zero?

Yes, dx/dt and d^2x/dt^2 can have negative or zero values. This indicates that the function is decreasing or has zero acceleration at that particular point in time, respectively. It is important to consider the sign of the derivatives when interpreting the behavior of a function.

5. How can the derivatives of a function be applied in real-life situations?

The derivatives of a function have various applications in real-life situations, such as in physics to determine the velocity and acceleration of an object, in economics to analyze the rate of change in a business or market, and in engineering to optimize the performance of a system. They can also be used in modeling and predicting future trends and behaviors.

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