[tex]\bf x=rcos(\theta )\implies \cfrac{x}{cos(\theta )}=r\\\\
y=rsin(\theta )\implies \cfrac{y}{sin(\theta )}=r
\\\\
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r=3cos(\theta )\implies \cfrac{x}{cos(\theta )}=3cos(\theta )\implies x=3cos(\theta )cos(\theta )
\\\\\\
\boxed{x=3cos^2(\theta )}
\\\\\\
r=3cos(\theta )\implies \cfrac{y}{sin(\theta )}=3cos(\theta )\implies \boxed{y=3cos(\theta )sin(\theta )}[/tex]
