If a straight line intersects a curve at two points, and the two points are infinitely close and tend to overlap, then the straight line is the tangent of the curve at that point. In junior high school mathematics, if a straight line is perpendicular to the radius of a circle and passes through the outer end of the radius of the circle, it is said that the straight line is tangent to the circle.
Tangency is the positional relationship between a circle on a plane and another geometric shape.
Here, when "another geometry" is a circle or a straight line, there is only one intersection point (common point) between them, and when "another geometry" is a triangle, there is only one intersection point between each side of the circle and the triangle. This intersection is the tangent point.
Basic definition
Tangency If a straight line and a curve intersect at two points, and the two points are infinitely close and tend to overlap, then the straight line is the tangent of the curve at that point. In junior high school mathematics, if a straight line is perpendicular to the radius of a circle and passes through the outer end of the radius of the circle, it is said that the straight line is tangent to the circle.
Concept introduction
Tangency is the positional relationship between a circle on a plane and another geometric shape.
Here, when "another geometry" is a circle or a straight line, there is only one intersection point (common point) between them, and when "another geometry" is a triangle, there is only one intersection point between each side of the circle and the triangle. This intersection is the tangent point.
Tangent property
If two circles are tangent, then the tangent point must be on the line.
location
Let the radii of two circles be r and r respectively, and the center distance ⊙ 1⊙2=d, then
(1) Are the two circles separate? d & gtR+r
(2) What are the circumscribed circles of two circles? d=R+r
(3) Do two circles intersect? r-r & lt； d & ltR+r(R≥r)
(4) Are the two circles inscribed? d=R-r
(5) What are two circles? 0≤d & lt； R-r。