## Calculus 8th Edition

The parametric equations of a circle whose radius is $r$ are given as follows: $x=r \cos t ; y =r \sin t$ From the given problem, we have $x= \cos t , y=\sin t, z=\cos 2t$ This implies that we have the projection of the curve on $xy$ plane is a circle having radius $1$. and the parametric equation $z=e^{0.8} t$ signifies that the value of $z$ is greater than $0$ for all $t$. This conclusion signifies the conditions indicated in the Graph(IV)