Question

how to solve dy/dx: cos*2X

Answer 1

derivative of cos (chain 2x)

Answer 2

sin2x*2

Answer 3

Are you sure, Starica is getting ready to correct you

Answer 4

awww i thought we r to find dy/dx :S

Answer 5

you just derive the outside and inside ^_^

outside = cos
inside 2x

so dy/dx of cos = -sin

and dy/dx of 2x = 2

soooo, dy/dx cos(2x) = -2sin(2x)

Answer 6

o_o... but wasn't she right?

Answer 7

no i missed the negative sign

Answer 8

isn't it finding the derivative of cos(2x)?

Answer 9

lol, it's alright :)

Answer 10

i guessed it so

Answer 11

you were close =P

Answer 12

thanks:p

Answer 13

np ^_^, do you get it now sandip?

Answer 14

no its finding the derivative of cos^2x

Answer 15

OH!

so the question is:

\[\frac{dy}{dx} \cos^2(x)\]?

Answer 16

ya

Answer 17

alright so we have 2 steps, first outside then inside, our outside here is the power and the inside is cos(x)

so dy/dx = - 2cos(x) sin(x) ^_^

Answer 18

but star ...dont u think it must b y= cos^2x n find dy/dx??

Answer 19

yeah lol

Answer 20

wasn't I right? o_o

Answer 21

... Go by the definition of the chain rule.

\[Let\ (cos\ x)^2 = f(g(x))\]

What is our f(x), what is our g(x)?

Answer 22

she/he doesn't get the chain rule >_< lol

Answer 23

in a much simpler way do it this way:

cos(x) . cos(x)

u'v + uv' ^_^ and solve

Answer 24

I hope this way helps though :)

Answer 25

alright gtg, later ^_^

Answer 26

he-she isn't going to be able to do any of the rest of their homework if they don't understand the chain rule. This is a good opportunity to learn the chain rule since you need it to solve this problem.

Answer 27

What can I say. Star likes manual labor.

Answer 28

lol, I'm just trying to get it clear for him/her ^_^?