Sorry, should have posted the whole question. f(x)=3secx find f''(pi/5). Thank you.
f(x) =3 sec x
f ' (x) = 3sec( x ) tan (x)
f '' (x) = 3[ sec (x) tan (x) * tan (x) + sec (x) * sec2 (x)]
So
f " (pi/ 5) = 3 [sec (pi/5) * tan2 (pi/5) + sec3 (pi/5 ]) = about 7.623
