Circles Question
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Given: The circle pictured with diameter ¯AD (not drawn), with ¯AB tangent to the circle, and line ¯AC also not drawn.
Prove: △ABD ~△CAD.

Statement | Reason |
1.Draw ¯AD & ¯AC | 1.Two points create a line |
2.¯AD is a diameter | 2.Given |
3.∠ACD is a right angle | 3.Inscribed angle subtended by a diameter is a right angle |
4.¯AB is tangent to the circle | 4. |
5.¯AB⊥¯AD | 5.A tangent line is perpendicular to the diameter |
6.∠BAD is a right angle | 6. |
7.∠ACD≅∠BAD | 7.All right angles are congruent |
8.∠ADC≅∠ADB | 8.Reflexive property |
9.△ABD ~△CAD | 9.AA |
- Looks correct; Definition of perpendicular lines
- Given; Triangle ABD is a right triangle
- Definition of a Tangent; Looks correct
- Given; Definition of perpendicular lines