How do you differentiate f(x) =cosx*sec^2(x) ?

2 Answers
Mar 7, 2016

d/(d x) f(x)=sec^2 x

Explanation:

d/(d x) f(x)=-sin x *sec^2 x+ 2secx*sec x*tan x*cos x
d/(d x) f(x)=-sin x *sec^2 x+ 2sec^2x*tan x*cos x
d/(d x) f(x)=sec^2(-sin x+tan x*cos x)" , "tan x=(sin x)/(cos x)
d/(d x) f(x)=sec^2 x(-sin x+(sin x)/cancel(cos x)*cancel(cos x))
d/(d x) f(x)=sec^2 x(cancel(-sin x)+cancel(sin x))
d/(d x) f(x)=sec^2 x

Mar 7, 2016

f'(x) = secxtanx. Here are two ways to get this answer.

Explanation:

Rewrite first

f(x)=cosxsec^2x

= cosx 1/(cosx)^2

= 1/cosx

= secx.

So,

f'(x) = secxtanx.

Use product rule first
f(x)=cosxsec^2x

f'(x) = (-sinx)(sec^2x)+(cosx)(2secx*secxtanx)

= -sinxsec^2x+2sec^2x [tanx cosx]

= -sinxsec^2x+2sec^2x [sinx]

= sec^2xsinx

= secx tanx