Question

how would i find the derivative of tanx-3cos5x?

Answer 1

do it in parts. First deal with tanx

Answer 2

so (sinx/cosx) ?

Answer 3

the derivative of tan is \[\sec ^{2}x\]

Answer 4

sure you could also do it that way

Answer 5

i know, but my teacher wants us using cos and sin identities right now

Answer 6

then use the quotient rule

Answer 7

have you learned the quotient rule?

Answer 8

yes, but using it with these kinds of problems is still not second nature, you know?

Answer 9

ya it will come with practice

it's bottom times the derivitave of the top plus top times the derivative of the bottom all over the bottom squared.

Answer 10

so i consider the top to be (sinx/cosx) and the bottom to be...?

Answer 11

so cosx(cosx)-sinx(sinx)/\[\cos ^{2}x\]

Answer 12

cos squared x?

Answer 13

you will consider the top to be sinx
and the bottom to be cos x

Answer 14

so in using the quotient rule, i only deal with tanx?

Answer 15

right that part goes on bottom
and the other part goes on top so cos squared minus sin squared on top

Answer 16

in using the quotient rule you deal with sinx/cosx

Answer 17

In any problem where you derive a function, you derive each term seperately. That's why you use the quotient rule on the sin(x)/cos(x) only. You'll just add the result of that to the derivative of 3cos(5x). Do you know the derivative of sin(x) and cos(x)?

Answer 18

you need to use the chain rule...See the linky...

http://www.wolframalpha.com/input/?i=derivative+of+tanx-3cos5x

Answer 19

and make sure you click on "Show the Steps"