find the derivative of y=xsec kx i thought since it was asking for dy/dx, that k would be zero since its a constant, but i was wrong.

Question

find the derivative of y=xsec kx  i thought since it was asking for dy/dx, that k would be zero since its a constant, but i was wrong.

laddiusmaximus · Answer

my answer was y' = (secx tanx)(sec kx) but I was a bit off.

anonymous · Answer

yes it is incorrect

it should be

y'=sec(kx)+x*(sec(kx)(tan (kx))*k

anonymous · Answer

product rule

laddiusmaximus · Answer

well the book has sec kx(kx tan kx +1)   i thought chain rule would be used, but the k is confusing me plus I dont know where the plus one came from

zepdrix · Answer

look at psi's answer a sec, :)
If you factor a sec(kx) out of each term, you get what the book has :D

anonymous · Answer

dont rely on books, they save space as it costs a lot for printing long expressions :)

anonymous · Answer

be self confident

laddiusmaximus · Answer

so product rule? I dont need to use the chain rule?

anonymous · Answer

both

laddiusmaximus · Answer

so product rule first, then chain rule?

anonymous · Answer

yes depends , how you use it though

anonymous · Answer

did you solved it yet? what answer you got?

anonymous · Answer

dy/dx=kx tan kx sec kx + sec kx