Help with derivatives and some general questions

AMonkeysBanana

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Sep 20, 2015
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This is cal 1, and man, I feel like I suck. I need to find dy/dx (derivative of y with respect to x, yeah?) of

y = xe^-x*secx

What rule do I use? If the rule isn't applicable do I just "take the derivative"? like cosx is y'=-sinx what rule is used :???:
For example in this problem,

y = 4tanx*secx - csc^2x

What rule is used? For csc^2x would I use the chain rule? And 4tanx*secx a different rule? I would think to use the difference rule, but I cant because "4tanx*secx"?

And just as a general question, do some derivatives involve say the product rule and then the power rule?
 
I need to find dy/dx (derivative of y with respect to x, yeah?) of

y = xe^-x*secx

What rule do I use?
Since this is a product, the use of the Product Rule would probably be helpful.

If the rule isn't applicable do I just "take the derivative"?
I'm sorry, but I don't know what this means...?

like cosx is y'=-sinx what rule is used
In order to do what? (This is already differentiated, so whatever the instructions might have been, they probably weren't to "find the derivative", is why I ask.)

For example in this problem,

y = 4tanx*secx - csc^2x

What rule is used?
What rule is used to do what? Find the derivative? You would apply the rules appropriate to each bit, as you encounter it. The first term is a product, so use the Product Rule. The second term is a composition (a trig function inside a square), so use the Chain Rule.

And 4tanx*secx a different rule? I would think to use the difference rule...
What is "the difference rule"? Since you do not have a difference inside this one term, how would a "difference rule" apply? On what logical basis?

but I cant because "4tanx*secx"?
You can't do what? Because the term... what? (This sentence appears to have been cut off before the conclusion of the thought...?)

And just as a general question, do some derivatives involve say the product rule and then the power rule?
Yes; different expressions will contain different terms and different functions in different combinations, and will therefore likely require different applications of different rules at different times. There is no one rule for every differentiation. ;)
 
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