Question

Find the third derivative of y = xsinx

Answer 1

What is the first derivative?

Answer 2

product rule?

Answer 3

my first derivative is y' = sinx +xcosx

Answer 4

y'' = 2cosx - xsinx

Answer 5

Bingo... now take the derivative of that for the second derivative.

Answer 6

bingo again.

Answer 7

one more time now

Answer 8

y''' = -2coxsinx - xcosx

Answer 9

y''' = -2cosxsinx - xcosx

Answer 10

oh wait

Answer 11

check it out

Answer 12

nope nut close try the 3rd derivative again

Answer 13

y''' = -2cosxsinx - xcosx - sinx

Answer 14

no so your y"=sinx + xcosx ... so what is the derivative of sinx? then what is the derivative of xcosx? then subtract each.

Answer 15

y'''= sinx+xcosx

Answer 16

Sorry I screwed up y"=2cosx - xsinx...let's go from there ok?

Answer 17

y'''= -3sinx+xcosx

Answer 18

There you go! Good job.