Math Help - [SOLVED] Derivate of cos(arctan x)

1. [SOLVED] Derivate of cos(arctan x)

How do you do this: d/dx[cos(arctan x)]

2. How would you differentiate $\cos\big(f(x)\big)$ ?

3. Originally Posted by Amberosia32
How do you do this: d/dx[cos(arctan x)]
Have a look at dot point 5 in Krizalid's sig.

4. cos(arctan(x)) = 1/sqrt(1+x^2) = (1+x^2)^(-1/2)

to see this draw a right triangle with an acute angle u whose opposite side is x and whose adjacent side is 1 making the
hypteneuse sqrt(1+x^2)

5. Thank you so much.