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Constructing the Tangents to a Circle in GeoGebra
     You can use GeoGebra to construct the tangents to a circle. The instructions are the same whether you construct the tangent at a point on the circle boundary, or you construct the tangents passing through a point outside the circle. 
     GeoGebra Instruction 1
- 1.
-          Open         Graphics ViewunderViewinMenu.
- 2.
-          Click         Tangentsby first clicking tool number 4, then tool number 5 in the drop-down list. 
- 3.
- Click on the point.
- 4.
- Click on the circle.