Question

evaluate the limit

lim cos(7x) -1 / x^2
x->0

Answer 1

so far i've done -7 sin 7x -1 / 2x

Answer 2

using the double angle formula,
we have \(cos 2\theta=1-2\sin^2\theta\)

Answer 3

need to use l hospital's rule to evaluate but i'm not sure how to work it out

Answer 4

no need for that.. just use the double angle formula

Answer 5

\[
L=\lim_{x\to0}\frac{1-2\sin^2\left(7x\over2\right)-1}{x^2}
\]

Answer 6

follow?

Answer 7

no I ended up with -7cos(7x) / 2 = 7/2

Answer 8

our whole point was to get the sine

Answer 9

use the equation editor below to enter your steps.

Answer 10

the answer is 49/2

Answer 11

i mean
-49/2

Answer 12

we are trying to create the form
\[
\lim_{x\to0}\frac{\sin x}{x}=1
\]

Answer 13

Thank you!