Question

Can you check my work please?
derivative of 2tan(x/2)-5

Answer 1

by letting u = (x/2)
y=f(u)=2tan(u)
dy/du=(2)(sec^2u)
du/dx=(1)
y=2sec^(u)
y' = 2sec^2(x/2) ?

Answer 2

not quite

Answer 3

yeah... because the answer is only sec^2(x/2)... can you tell me where i went wrong?

Answer 4

you forgot to cancel out the 2

Answer 5

the 2? mmm, you mean the 2 and the x/2?

Answer 6

wait a sec

Answer 7

ok

Answer 8

\[ u = \frac{x}{2} = \frac{du}{dx} = \frac{1}{2}\]
\[y = 2 tan(u) - 5 => \frac{dy}{dx} = 2sec^{2}(x/2) * \frac{1}{2}\]
\[ \frac{dy}{dx} = sec^{2}(x/2)\]

Answer 9

ok this is some chain rule which i cant remmeber

Answer 10

@Miracrown: what do you think?

Answer 11

mim, i think a lot :P

Answer 12

ahhh yes yes. now i get it. :)

Answer 13

thanks :D gonna post another problem.

Answer 14

:)