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Let’s Review some old vocabulary Let’s Review some old vocabulary. Line segments are congruent if they are the same length. Assuming this ruler is 6” long, we measure the bottom segment and get 6”. Measuring the second segment we also get 6” so we know that these segments are congruent.

50 ⁰ 50 ⁰ Congruent angles are angles that have the same measure. Using protractors, we find that they each measure 50 degrees; therefore, they are congruent.

We know that parallel lines never intersect so if we take a ruler to any corresponding points on line a and line b we should find that they are the same distance apart. These lines are parallel.

A B C D A’ B’ C’ D’ We’re going to slide parallelogram ABCD to the right. The mathematical term for sliding shapes, left, right, up, or down is “translating.” After we translate the parallelogram to the right, it will create a new version of the shape, A’B’C’D’. The ‘ notation signifies that A has moved to a new location called its “image.” After the translation we’ll investigate what changed and what stayed the same. 

A B C D A’ B’ C’ D’ We’ll place the ruler on AD and mark its length. Then slide across to see if A’D’ has the same length. We’ll do the same with BC and B’C’

A B C D A’ B’ C’ D’ We’ll use the same procedure for AB and A’B’ then CD and C’D’

75 ⁰ 105 ⁰ A B C D A’ B’ C’ D’ 75 ⁰ 105 ⁰ 75 ⁰ 105 ⁰ 75 ⁰ 105 ⁰ Angle A is 75 degrees. If I slide this measurement over to angle A’ I see that it matches. We’ll do the same for angles B, C and D.

A B C D A’ B’ C’ D’ First we’ll extend the segments in both directions on parallelogram ABCD and see if the distances are the same on either side.

A B C D A’ B’ C’ D’ Preserving parallelism simply means that if the lines were parallel in the original shape, then they would still be parallel in the image. We’ll perform the same parallel test on this image to see if the lines are still parallel in the image.

A B C D A’ B’ C’ D’ Read slide

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