Presentation on theme: "Circles: The Length of Tangent/Secant Lines"— Presentation transcript:
1 Circles: The Length of Tangent/Secant Lines Endpoint outside the circle…
2 Secant and Tangent Lines If part of secant line is outside circle, call it the “external segment.”ADA = Secant LineDC = Tangent LineDB = External Segment of the Secant Line.BDC
3 Secant and Tangent Lines The square of the tangent line is equal to the product of the external segment and the whole secant line.(Tangent)2 = External Segment(Secant Line)A(DC)2 = DB(DA)BDC
4 Example 8 x Secant: DA = 20 Ext. Seg: DB = 8 (DC)2 = DB(DA) To find an unknown length: Use a variable.Substitute the values you know.Simplify.Secant: DA = 20Ext. Seg: DB = 8A(DC)2 = DB(DA)B8(x)2 = 8(20)DxC
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