derivatives with trig equations question..

[ihatecalc]

okay, so i know that the derivative of (sec x) is (sec x tan x)

so, when my homework question told me to find the derivative of (x sec x) i put (x sec x tan x) but the real answer is (x sec x tan x + sec x).

i do not understand where the second (sec x) comes from.

if someone could explain this for me, i would be very greatful!

 

[stapel]

Has your class covered the Product Rule yet?

Thank you.

Eliz.

 

[mathstresser]

The product rules is 1D2 +2D1 (first times the deriviative of the second plus the second times the derivative of the first)

x sec x

(x)(secxtanx) + sec x(1)=

xsecxtang + secx