Question

derivative of y = sin2x cos2x

Answer 1

write it as y= sin4x/2 , then find the derivative using chain rule :)

Answer 2

can you teach me how to solve that?

Answer 3

@Dexter810

Answer 4

yes :)
See , the chain rule is applied when you are differentiating with something other than x ..like x^2 or say , 5x+3 .

Answer 5

Now , you differentiate your function with respect to the other function that is not x , multiply it with the derivative of ' the other function that is not x' with repect to x

Answer 6

I hope you undertood what i am trying to say , give it one shot :)

Answer 7

[ 1/2 sin4x ] ' = 1/2 cos4x * 4 ?

Answer 8

The product rule is unnecessary here. Use the sine double angle formula: sin (2u) = 2 sin u cos u.

Thus y(x) = (1/2) sin(4x).

y'(x) = (1/2) cos(4x) * 4 = 2 cos (4x).

Answer 9

^ @zephy thats exactly what was done and suggested .

Answer 10

@zephy @Dexter810 can you teach me . how it become y = (1/2) sin 4x

Answer 11

Yes @jayryan021 ! Exactly :)

Answer 12

You can derieve that using the first principle , the proof can be found in any book :)

Answer 13

okay thanks for answering my question :)

Answer 14

You can watch it from this video too :
https://www.youtube.com/watch?v=ojNz3Yd-mnI
No problem :)