How to Find Coefficient of x^4 in Maclaurin Series for e^sinx?

In summary, the task is to find the coefficient of x^4 in the MacLaurin series for the function f(x) = e^sinx. The conversation suggests using the expansion for sin x and e^y to simplify the derivatives, rather than finding them individually. This involves plugging in the expansion for sin x and collecting the terms, up to the fourth order.
  • #1
jnimagine
178
0

Homework Statement


find coefficient of x^4 in the MAclaurin series for f(x)=e^sinx


Homework Equations


ok... so taking derivatives 4 times for this function...gave me a mess! @.@
can someone help me in simplying the derivatives...?
1. cosxe^sinx
then for 2. is it -sinxe^sinx-sinxcosxe^sinx...?
= . = I'm getting lost with these derivatives...

same for e^3xcos2x... gets sooo complicated...
 
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  • #2
Don't try to find it by determining the derivatives. You already know the expansions of the function sin x and e^y. Just plug them in, and expand up till 4th order (or better to just look what terms contribute to the x^4 coefficient).

E.g.:
[tex]e^{\sin x} = \sum_{k=0}^\infty \frac{(\sin x)^k}{k!}[/tex]

Then plug in the expansion for sin x and collect the terms.
 
  • #3
xepma said:
Don't try to find it by determining the derivatives. You already know the expansions of the function sin x and e^y. Just plug them in, and expand up till 4th order (or better to just look what terms contribute to the x^4 coefficient).

E.g.:
[tex]e^{\sin x} = \sum_{k=0}^\infty \frac{(\sin x)^k}{k!}[/tex]

Then plug in the expansion for sin x and collect the terms.

hmm I'm still not too sure...
I do get the series u've written above... now for sinx i expand it like x - x^3/3! + x^5/5!... up to the fourth order... and plug in 0??... doesn't that just make everything equal to 0...?
 
  • #4
I think what xepma is talking about is this[tex]e^{\sin x} = \sum_{k=0}^\infty \frac{(\sin x)^k}{k!}[/tex]
[tex]= 1 + sin(x)/1 + sin^2(x)/2 + sin^3(x)/3! + ...[/tex]

Now, put in your series for sin(x), sin2(x) and so on. You probably won't need the sin3(x) and might need only a term or two for the sin2(x) part.
 

1. What is a Maclaurin series coefficient?

A Maclaurin series coefficient is a numerical value that represents the coefficient of a term in a Maclaurin series, which is a type of power series expansion of a function around a specific point, usually x=0. It is used to approximate a function and can be calculated using a specific formula.

2. How do you calculate the Maclaurin series coefficient?

The Maclaurin series coefficient can be calculated using the formula: f^n(0)/n!, where f^n(0) represents the nth derivative of the function at x=0 and n! is the factorial of n. This formula can be used to find the coefficient for any term in the series.

3. What is the significance of the Maclaurin series coefficient?

The Maclaurin series coefficient is significant because it allows us to approximate a function using a series of polynomials, which can make complex functions easier to work with. It also helps us understand the behavior of a function and can be used to find specific values of the function at a given point.

4. Can the Maclaurin series coefficient be negative?

Yes, the Maclaurin series coefficient can be negative. The sign of the coefficient depends on the function and the specific term in the series. It is important to pay attention to the sign of the coefficient when using the Maclaurin series to approximate a function.

5. How is the Maclaurin series coefficient related to Taylor series coefficients?

The Maclaurin series is a special case of the Taylor series, where the series is centered at x=0. Therefore, the Maclaurin series coefficient is also a Taylor series coefficient for a specific term in the series. However, the Taylor series allows for expansion around any point, while the Maclaurin series is limited to the point x=0.

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