Question

Finding second derivative of
y=7xsinx
u=7x v=sinx
u'= 7 v'= cosx

u'v+v'u
7*sinx +cosx* 7x

y' =(7)sinx+(7x)cosx


y'' = 7cosx + -sinx (7x)+7cosx
// I don't understand why the 7cosx is there :S

Answer 1

let me show you in details

Answer 2

this is wrong y' =7sinx+cos(7x)

i think you meant 7xcos(x)

Answer 3

you just got a bit confused

Answer 4

are you there?

Answer 5

yes, i see.

Answer 6

always write the x's before the trig function so you don't get an error