# Math Help - differentiating y=tan(u*pi)

1. ## differentiating y=tan(u*pi)

tan (u*pi)=sec^2(u)(pi) = pi*sec^2 (pi*x)

i understand how the derivative would be sec^2u times pi, but how does that multiplication give

pi*sec^2pi*x

where did the x come from?

sec^2u times pi[/tex] is equal to [tex]pi*sec^2 (pi*x) ?

PS I tried wrapping this in [tex] but it came up with all kinds of errors for some reason, let me know if its too crappyly written and i'll find a way to re-write it (im out of time at the mo or I'd rewrite it now)

2. ## Re: differentiating y=tan(u*pi)

this is a picture of the answer the question was

y=tan pi x

where did the second pi and x come from?

3. ## Re: differentiating y=tan(u*pi)

$\frac{d}{du}\left(\tan(\pi u) \right)=\sec^2(\pi u)\frac{d}{du}(\pi u)=\pi\sec^2(\pi u)$

4. ## Re: differentiating y=tan(u*pi)

thanks! i see now, I was not including sec^2(pi*u), i was just multiplying by sec^2 of nothing