Question 1137289
<br> 
Square the expressions for both x and y and then use the Pythagorean identity<br>
{{{sin(x)^2+cos(x)^2 = 1}}}<br>
{{{x^2 = 9sin^2(3t)}}}
{{{y^2 = 9cos^2(3t)}}}
{{{x^2+y^2 = 9(sin^2(3t)+cos^2(3t)) = 9(1) = 9}}}<br>
The equation is<br>
{{{x^2+y^2 = 9}}}<br>
which you surely know is a circle with center at the origin and radius 3.