Posted by **CMM** on Sunday, October 24, 2010 at 11:17pm.

If f(x)= sec x, find f"(Pi/4)

I am not sure how to take the 2nd derivative?

f'(x)= sec x tan x

f"(x)=???

Is it f"(x)= (sec x tan x)(sec^2x)???

Please Help!

- Calc -
**Reiny**, Sunday, October 24, 2010 at 11:24pm
f'(x)= sec x tan x is correct

now use the product rule

f''(x) = secx(sec^2x) + tanx(secx)(tanx)

= sec^3 x + secx(tan^2x)

I will leave the subbing to you

- Calc -
**Chelsea**, Monday, October 25, 2010 at 1:55am
What do you mean subbing? I thought that was the final answer? In the book it leaves f"(x)= - cos x for f(x)= cos x

- Calc -
**Chelsea**, Monday, October 25, 2010 at 2:08am
Oops, sorry about that. Do you mean this:

sec^3(Pi/4) + sec(Pi/4)(tan^2(Pi/4)) =

3*sqrt(2)

## Answer this Question

## Related Questions

- Integration - Intergrate ¡ì sec^3(x) dx could anybody please check this answer. ...
- Calculus 12th grade (double check my work please) - 2- given the curve is ...
- calculus - find dy/dx y=ln (secx + tanx) Let u= secx + tan x dy/dx= 1/u * du/dx ...
- calculus (check my work please) - Not sure if it is right, I have check with the...
- Calculus - could anybody please explain how sec x tan x - ¡ì sec x tan^2(x) dx...
- Calculus AP - I'm doing trigonometric integrals i wanted to know im doing step ...
- calculus - So I am suppose to evaulate this problem y=tan^4(2x) and I am ...
- Calculus PLEASE check my work , - 1.) which of the following represents dy/dx ...
- Calculus 1A - I am trying to find: dy/dx for y = sec(tan x) I have the answer, ...
- Calculus 12th grade (double check my work please) - 1.) which of the following ...

More Related Questions