Question 1137703
.
<pre>
x = 3 cos t, 

y = 3 sin t


Square both equations and then add them. You will get


{{{x^2}}} + {{{y^2}}} = {{{9*cos^2(t)}}} + {{{9*sin^2(t)}}} = {{{9*(sin^2(t) + cos^2(t))}}} = 9.


Thus finally your equation is


{{{x^2 + y^2}}} = 9.     (1)


It is the equation of the circle of the radius 3 units centered at the origin of the coordinate system at (x,y)-coordinate plane.


Thus the parameter  " t "  is just eliminated, and the result is the equation (1).
</pre>

Solved, explained and completed.



==============



By the way, this your post is a duplicate.


It was posted to the forum  3 - 4 days ago, and I and @greenestamps just answered it.


So, I do not understand what was the meaning of posting it again.