Question

If y=4cos(2x) then d^2y/dx^2=?
A.-8cos2x
B.16cos2x
C.-32cos2x
D.-4cos2x
E.-16cos2x

Answer 1

You should be able to do that one with the help I gave you on the last one, just chain rule and product rule. I'll tell you if you get it right though. :P

Answer 2

But it's squared :O is it still the same ?@Mikogekz

Answer 3

d^2y/dx^2 is just the second derivative, all you need to do is take the derivative of the derivative.

Answer 4

My first derivative is 4cos2x-88sin2x

Answer 5

Only one 8 @Mikogekz

Answer 6

-8sin2x is the first derivative.

Answer 7

\[y=4\cos(2x)\]
\[\frac{dy}{dx}=\frac{d(4\cos(2x))}{dx}\]

\[=4\frac{d(\cos2x)}{dx}\]

\[=4[(-\sin2x)(2)]=-8\sin(2x)\]


\[\frac{dy}{dx}=-8\sin(2x)\]

\[\frac{d^{2}y}{dx^{2}}=-8\frac{d(\sin2x)}{dx}\]

\[=-8(\cos(2x)(2))=-16\cos(2x)\]

Answer 8

nope its E...

Answer 9

Forgot it was negative oops yup it's E

Answer 10

Thanks again @miko