The standard form of a circle is equal to x^2 + y^2 = r^2. As this equation shows x^2 + y^2 = 16, all we have to do is find the square root of 16, which is 4. This means that 4 is the radius of the circle and that 2 * 4 = 8, which is the diameter of the circle.
<u>Because of this, the diameter of this circle is equal to 8.</u>
