$\"\"$

The parametric equations of an circle equation are $\"\"$ and $\"\"$ .

Eliminate the parameter $\"\"$ .

Consider $\"\"$ .

$\"\"$

Consider $\"\"$ .

$\"\"$

$\"\"$ .

Pythagorean identity : $\"\"$ .

Substitute $\"\"$ and $\"\"$ .

$\"\"$

$\"\"$ .

The standard form of an circle equation is $\"\"$ with center $\"\"$ and radius $\"\"$ .

$\"\"$

The standard form of an circle equation is $\"\"$ .