Solving for Higher Order Derivatives: Explaining f(x)=cos2x and f^50 = f^2

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In summary, high order derivatives are the derivatives of a function that have been taken multiple times, representing the rate of change of the rate of change of the original function. They can be calculated using the same methods as regular derivatives, but are taken multiple times. High order derivatives are significant in providing more detailed information about a function's behavior and are important in physics and engineering. They also play a crucial role in determining the accuracy of Taylor series approximations. High order derivatives can be negative, indicating a decreasing rate of change in the function.
  • #1
dimpledur
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Homework Statement



if f(x)=cos2x, how do we know that f^50 = f^2 ??

In the solution it states that because 50 = (12)(4) + 2, then f^50 = f^2.

What the??
 
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  • #2
We don't know that f(50) = f(2) for the reason that it isn't true. If the function were f(x) = cos(x), it would be true, though, and this is easy enough to verify by taking a few derivatives and noticing the cyclical nature of these derivatives.
 
  • #3
Okay, well how do they know that f^2 = f^50 for cosx simply by going 50 = (4)(12) + 2
 
  • #4
Because it repeats every four times
cosx
-sinx
-cosx
sinx
cosx
 

1. What are high order derivatives?

High order derivatives refer to the derivatives of a function that have been taken multiple times. They represent the rate of change of the rate of change of the original function.

2. How are high order derivatives calculated?

High order derivatives can be calculated using the same methods as regular derivatives, such as the power rule or the product rule. The only difference is that the derivative is taken multiple times, depending on the order.

3. What is the significance of high order derivatives?

High order derivatives can provide more detailed information about the behavior of a function, such as the curvature or inflection points. They are also important in fields such as physics and engineering, where higher order derivatives represent acceleration and other important quantities.

4. How do high order derivatives relate to Taylor series?

Taylor series is a mathematical tool used to approximate a function with an infinite series of derivatives. High order derivatives play a crucial role in determining the accuracy of this approximation, as the higher order terms are often what contribute to the error.

5. Can high order derivatives be negative?

Yes, high order derivatives can be negative. This means that the function is decreasing at an increasing rate. For example, if the second derivative is negative, the function is concave down, and if the third derivative is negative, the function is concave down at an increasing rate.

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