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## Main Question or Discussion Point

id like some help deriving certain functions using the chain rule

the way our teacher does it is different from what the textbook says

he derives the outermost functions before getting to the innermost functions, this is where

i get confused =(

for example

f(x) = sincos(5x)

i get

f'(x) = (coscos(5x)) (-sin(5x)) (5)

= -5coscos(5x)sin(5x)

im not sure if this is right

another question:

f(x) = sin^4(2x) + cos^4(2x)

the way our teacher does it is different from what the textbook says

he derives the outermost functions before getting to the innermost functions, this is where

i get confused =(

for example

f(x) = sincos(5x)

i get

f'(x) = (coscos(5x)) (-sin(5x)) (5)

= -5coscos(5x)sin(5x)

im not sure if this is right

another question:

f(x) = sin^4(2x) + cos^4(2x)