This applet lets you explore congruent angles formed by parallel lines with transformations.

1) Are the lines parallel? How do you know? 2) Drag points B and C to show that lines remain parallel. 3) Click “Step 1.” What transformation maps <HBD onto <H’BD’? a) 180o Rotation b) Reflection c) Translation 4) Click “Step 2.” What transformation maps <D’BH’ onto <D”CH”? a) 180o Rotation b) Reflection c) Translation 5) Click “Step 3.” What transformation maps <D”CH” onto <D’’’CH’’’? 6) a) 180o Rotation b) Reflection c) Translation 7) Drag points B and C to show that angles remain congruent. Drag points D and H to show that the transformations maintain congruence. EXAMPLE: Write a paragraph proof. Prove that <1 is congruent to <3 using transformations. A 180o Rotation maps <1 onto <2 therefore <1 <2. A translation maps <2 onto <3 therefore <2 <3. By transitive property <1 s congruent to <3. 8) Write a paragraph proof, using transformations, proving <2 s congruent to <4.