Posted by **Sam** on Tuesday, June 10, 2008 at 10:58pm.

Can someone help me find the derivatives of these questions?

For these can you only need to tell me the answer so i can see if i have the same thing.

y=cos(-4x)

y = sinx^2

y = xcosx

I need help with these 6 please.

y = xcos(1/x)

y = (1+sinx)/(1-sin^(2)x)

y = sin^2x/cosx

y = sqrt(sin(sqrtx))

y = 3sqrt(xcosx)

y = 1/(sin(x-sinx)

- Calculus -
**Reiny**, Wednesday, June 11, 2008 at 12:02am
y=cos(-4x)

y' = -4(-sin(-4x)

= 4sin(-4x)

y = sinx^2 or (sinx)^2

y' = 2sinxcosx or sin 2x

y = xcosx

y' = x(-sinx) + (1)cosx

= cosx - xsinx

- Calculus -
**Reiny**, Wednesday, June 11, 2008 at 12:08am
for y = xcos(1/x)

I would use the product rule

y' = x(-sin(1/x))(-1/x^2) + (1)cos(1/x)

for y = (1+sinx)/(1-sin^(2)x) I would reduce it to

y = (1+sinx)/((1+sinx)(1-sinx))

= 1/(1-sinx)

= (1-sinx)^-1

now y' = -1(1-sinx)^{-2?sup>(-cosx)
why don't you show me some of the steps you have sofar for the others?
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