# Math Help - Existence of Derivative

1. ## Existence of Derivative

Hello i have the following exercise:

$x(t) = \frac{3}{t^3}$

and

$y(t) = e^{tan(t)}$

for which $t$ does the first derivative exists ?

2. Originally Posted by coobe
Hello i have the following exercise:

$x(t) = \frac{3}{t^3}$

and

$y(t) = e^{tan(t)}$

for which $t$ does the first derivative exists ?
$\mid t \mid \ne 0$

3. for y(t)

dy/dt = e^tan(t) sec^2(t)

is defined except for odd multiples of pi/2 --> (2n-1)pi/2 for all integers n. as tan(t) and sec(t) are not defined at these points