**EMAT
6700**

**by
Brad Simmons**

**Tangent from a Point Outside the Circle**

Use geometer's sketchpad to construct a tangent line from a point outside the circle.

**Construct a line tangent to a given circle C through a
point A outside the circle.**

1. Construct segment AC.

3. Construct the midpoint of segment AC. Label the midpoint M.

4. Construct segment CM. Select midpoint M and segment CM. Construct circle by center and radius.

5. Label the intersections of the two circles point D and point E.

6. Select circle M. Select segment CM and segment AC. Select midpoint M. Hide the objects. Construct line AD.

**Line
AD is tangent to circle C. Furthermore, line AE is also tangent to circle
C.**

Please click here for a geometer's sketchpad sketch of the figure shown above.

Please click here for more information about constructing common tangents to circles.