# parametric equation for tangent line

• Oct 20th 2009, 04:30 PM
dat1611
parametric equation for tangent line
r(x)=(e^xsin(x), e^x, e^xcos(x))

find the parametric equations for the tangent line at x=0 and pi/2
can someone help me with this
• Oct 20th 2009, 05:47 PM
Quote:

Originally Posted by dat1611
r(x)=(e^xsin(x), e^x, e^xcos(x))

find the parametric equations for the tangent line at x=0 and pi/2
can someone help me with this

Did you state the equation exactly as it was given? This written in an unusual way. Usually the nation for an equation like this is:

$r(t)=< e^{tsin(t)},e^t,e^{tcos(t)} >$

where t is the parameter. The parametric equations for the curve are:

$x =e^{tsin(t)}$

$y=e^t$

$z =e^{tcos(t)}$

So I take it that you are trying to find the equation of the tangent line corresponding to the parameters t=0, and then the tangent at $t=\frac{\pi}{2}$ correct?

The components of the derivative of a vector function are the derviatives of the components.

$r'(t)=< \frac{dx}{dt},\frac{dy}{dt},\frac{dz}{dt} >$

Now just plug in the given parameters.