Tangents and Secants of a Circle Definition of
- Slides: 9
Tangents and Secants of a Circle
Definition of Tangent A line, line segment, or ray is tangent to a circle if it intersects the circle in exactly one point. Segment CD is tangent to O C D circle O at point D. E Point of tangency
If a line is tangent to a circle, then it is perpendicular to the radius at the point of tangency. Segment CE is tangent to circle O. Point D is the point of tangency. O C D Segment OD is perpendicular to segment CE. E
If a line is perpendicular to a radius of a circle, then the line is a tangent of the circle. Segment DE is perpendicular to radius OD. Therefore segment DE is a tangent. O C D E
If two segments from the same exterior point are tangent to a circle, then they are congruent. Both tangents start at point A. AC and AB are congruent. C 5 A If AB = 5, then AC = 5. 5 B
If two secant lines intersect inside of a circle, you can find the measure of the created angle by adding the two minor arcs and dividing by 2. C O D B E A
If two secant lines intersect outside of a circle, you can find the measure of the created angle by subtracting the minor arc from the major arc and divide by 2. C B O D A E
If a tangent line and a secant line intersect outside of a circle, you can find the measure of the created angle by subtracting the minor arc from the major arc and divide by 2. B O D C E
If two tangent lines intersect outside of a circle, you can find the measure of the created angle by subtracting the minor arc from the major arc and then divide by 2. C O D E
