# calculus

posted by .

Use division of power series to find the first three terms of the Maclaurin
series for y = sec x.

• calculus -

There are different ways of doing the division. A method closely related to long division is to write down the general form of the answer in terms of undetermined coefficients and then multiply both sides by the numerator and then solve for the coefficients by equating equal powers of x.

In this case, we can put:

1/cos(x) = a0 + a2 x^2 + a4 x^4 + a6 x^6+...

We know that the function is an even function, so we only have even powers of x. Multiply bot sides by cos(x):

1 = [a0 + a2 x^2 + a4 x^4 + a6 x^6+...]
[1 - x^2/2 + x^4/4! - x^6/6! + ...] =

a0 + (a2 - a0/2)x^2 +
(a4 - a2/2 + a0/4!) x^4 +
(a6 - a4/2 + a2/4! - a0/6!) x^6 + ..

The constant term has to be 1:

a0 = 1

The coefficient of x^2 has to be zero:

a2 - a0/2 = 0 -->

a2 = a0/2 = 1/2

The coefficient of x^4 has to be zero:

a4 - a2/2 + a0/4! = 0 -->

a4 = a2/2 - a0/4! = 1/4 - 1/4! = 5/24

The coefficient of x^6 has to be zero:

a6 - a4/2 + a2/4! - a0/6! = 0 --->

a6 = a4/2 - a2/4! + a0/6! = 61/720

• calculus -

tinyurl slash x x 2 3 5 h j

## Similar Questions

1. ### Calculus

Obtain the MacLaurin series for 1/(2-x) by making an appropriate substitution into the MacLaurin series for 1/(1-x). ------------ The MacLaurin series for 1/(1-x) = Σ x^k I substitue (x-1) in for x, because 1/(2-x) = 1/(1-(x-1)) …
2. ### calculus

How do you differentiate the maclaurin series for 1/(1-x) twice to find the maclaurin series of 1/(1-x)^3.
3. ### calculus

Use multiplication of power series to find the first three non-zero terms of the Maclaurin series of e^x ln(1 − x).
4. ### Calculus

Find a power series, centered @ x=0, for function f(x)=x/(1+2x). I know this is a maclaurin series, but my work doesn't get the right answer. Can you please show steps?
5. ### Calculus

Find a power series, centered @ x=0, for function f(x)=x/(1+2x). I know this is a maclaurin series, but my work doesn't get the right answer. Can you please show steps?
6. ### Calculus Derivative- Taylor Series?

let f(x)= x/x-1 find f'(x) f ''(x) and a formula for f ^ (n) * x. I found the first and second derivatives but do not know how to make a general equation for this. I have not learnt the Taylor or Maclaurin Series either. Thank you.
7. ### Calculus II

So I have Maclaurin series for sinx = ∑(-1)^n[x^(2n+1)]/(2n+1)!. I need to write out new series for sin(x^2). This will be equivalent to squaring the whole Maclaurin series of sinx, right?
8. ### Integral Calculus

We can use this power series to approximate the constant pi: arctan(x) = (summation from n = 1 to infinity) of ((-1)^n * x^(2n+1))/(2n+1) a) First evaluate arctan(1) without the given series. (I know this is pi/4) b) Use your answer …
9. ### Calculus

The prompt for all of these question is "consider the function f(x) = sin^2(x)". Part A: Write the first four terms of the Maclaurin series for f(x). I assumed this implied non-zero terms, so I found x^2-(1/3)x^4+(2/45)x^6-1/315(x^8). …