Trig functions that i have to memorize?

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Homework Help Overview

The original poster is studying calculus and math 12 simultaneously, focusing on limits involving trigonometric functions. They express uncertainty about which trigonometric functions are essential to memorize, particularly in the context of evaluating limits.

Discussion Character

  • Exploratory, Conceptual clarification, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the importance of memorizing derivatives of trigonometric functions and suggest using L'Hopital's Rule for evaluating limits. The original poster questions which specific trigonometric functions are necessary for their studies.

Discussion Status

Some participants have provided guidance on derivatives and suggested methods for approaching the limit problem. There is an ongoing exploration of different strategies, including the application of L'Hopital's Rule and understanding specific limits involving sine and tangent functions.

Contextual Notes

The original poster indicates a lack of familiarity with trigonometric limits and derivatives, which may affect their ability to engage with the material effectively. There is an implied need for foundational knowledge in trigonometric identities and limits.

gillgill
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I am taking calculus and math 12 at the same time. Now we are doing limits of trigonometric functions, but i know nothing about it. What are some important trig functions that i have to memorize?

Ex. I have no idea how to do these
lim (tanx-sinx)/xcosx
x->0
 
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Your book probably has a table of the concepts you need such as.

d(x)sinX = cosX
d(x) cosx = -sinx
d(x) tanx = sec^2x
d(x) secx = secx tanx
d(x) cotx = -csc^2x
d(x) cscx = -cscx cot x

Are these what you were looking for?
 
To do that limit, you should use L'Hopital's Rule.

[tex]\lim_{x\rightarrow\infty} \frac{\tan0 - \sin0}{0*\cos0}[/tex] is indeterminate... you get 0/0. Differentiate the top and the bottom and try the limit again. If that doesn't work, then try it once more... If this continues to fail, use another approach.

Jameson
 
Know how to find the limit of sinx/x as x-> 0, the other trig identities don't need much thought, usually rearranging or using trig identities yields you an easy limit.
 

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