Trig functions that i have to memorize?

[gillgill]

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

 

[Zach_C]

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?

 

[Jameson]

To do that limit, you should use L'Hopital's Rule.

$$\lim_{x\rightarrow\infty} \frac{\tan0 - \sin0}{0*\cos0}$$ 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

 

[whozum]

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.