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# differentaiting trig with quotient rule watch

1. this is the question, find the gradient of the curve when x=0 the answer is -4

i used the quotient rule

i did

i then attempted to cancel

can some show me a full solution
2. this is wrong in a few places The most obvious way is the (tan(x))^2 - (sec(3x))^2, you do realise how that is wrong, right?

I would advise doing this again systematically and carefully

let u = tan(3x) +cos(2x)
v = ... etc
finding u' and v'

and then use the quotient rule.
3. is not

edit: too late
4. Note:

If you are only differentiating to find the gradient at x=0, there is no requirement to "tidy up" the derivative. Once you have it in the raw form, just substitute straight away.

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Updated: February 13, 2010
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