when two circles are defined in the same flat, we can analyze the positions that one of them occupies in relation to the other. Thus, the relative positions between two circles they are: disjoint, tangents and drying.
Disjoint Circumferences
Two circles are called disjoint when they have no common points. There are two cases to consider regarding this positionrelative between the circles:
1 – External disjoint circumferences
Two circles they are disjointexternal when they have no common point and, at the same time, when one of them is in the outer region of the other. The following figure shows examples of outer disjoint circles.
THE distance between the centers of circles external disjoints will always be greater than the sum of their radii. If this distance is equal to or less than the sum of the radii, the circles have points in common.
2 – Internal disjoint circumferences
Two circles are disjoint internal when they do not have points in common and, at the same time, when one is in the internal region of the other, as shown in the following figure.
The difference between the radii of these circles it will always be greater than the distance between the centers of the two.
Tangent Circumferences
Two circles are called tangents when they have a single point in common. Tangent circles can also be classified as inner or outer.
1 - Two circles they are tangentsexternal when they have a single point in common and, moreover, one of them is in the outer region of the other.
2 - Two circles they are tangentsinternal when they have a single point in common and, moreover, one of them is in the inner region of the other.
The following image shows examples of circles tangentsinternal and tangentsexternal.
Note that the circlestangentsexternal have the following characteristic: the sum of their radii is equal to the distance between their centers. In internal tangents, the difference between their radii is equal to the distance between their centers.
Drying Circumferences
Two circles are called drying when they have only two points in common.
