Help I Need To Find The Derivative

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    Derivative
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Homework Help Overview

The discussion revolves around finding the derivative of the function cos(8θ), which falls under the subject area of calculus, specifically differentiation techniques.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • The original poster expresses uncertainty about whether to use an identity or expand the function. Some participants inquire about the chain rule and suggest using it directly without expansion.

Discussion Status

The conversation includes various suggestions regarding the use of the chain rule for differentiation. Participants are exploring different interpretations of the problem, with some emphasizing that expansion is unnecessary.

Contextual Notes

The original poster seems to be grappling with the application of differentiation rules and the potential use of trigonometric identities, indicating a need for clarification on these concepts.

portillj72
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Help I Need To Find The Derivative!

I don't know how to find the derivative of cos(8theta)

i know there is an identity cos(2theta) but idk if I am able to expand it or not?
 
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Are you familiar with the chain rule?
 


Just make 8theta a function, then use the general power, or chain rule to differentiate. in other words you want to find dy/dtheta. So using the general power rule, or chain rule, the derivative=-sin(8theta)*(8theta')=-8sin(8theta)
 


nicksauce and poopcaboose are both saying that you don't need to expand it at all- just use the chain rule.
 

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