The radius of the circle decreases when you make the circle smaller.
The standard equation of a circle, with center in (a,b) and radius r, is: (x-a)2 + (y-b)2 = r2
There is no such thing as a standard equation. Furthermore, there are standard forms - all different - for the equation of a line, a circle, a plane, a parabola, an ellipse and so on. the question needs to be more specific.
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Standard equation for a circle centred at the origin is x2 + y2 = r2 where r is the radius of the circle. If you increase the size of the circle then the radius must increase, so r2 will be larger. eg a circle of radius 2 has the equation x2 + y2 = 4, if the radius increases to 3 then the equation becomes x2 + y2 = 9
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The Radius
Area of a circle = pi*radius squared Circumference of a circle = 2*pi*radius or diameter*pi
The Pythagorean theorem is used to develop the equation of the circle. This is because a triangle can be drawn with the radius and any other adjacent line in the circle.
it becomes a circle
(x - A)2 + (y - B)2 = R2 The center of the circle is the point (A, B) . The circle's radius is ' R '.
If you are referring to a circle, divide the diameter by 2 (to get the radius), then use the standard equation for the area of a circle. For your reference, this is the equation: area = pi x radius2