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Geometry Section 4-2AGeometry Section 4-2A

Correspondence and Correspondence and CongruenceCongruence

Pg. 256 – Pg. 256 – Please get your book.Please get your book.

Wednesday, you will need a ruler (cm) Wednesday, you will need a ruler (cm) and protractor.and protractor.

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Consider:Consider:Which figures are Which figures are congruent? Why?congruent? Why?

For the pairs of congruent figures, what transformations are necessary to move one figure so that it coincides with the other?

Pg. 256

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The 2 triangles on page 256 are The 2 triangles on page 256 are congruent. Measure the segments and congruent. Measure the segments and angles to find the corresponding parts.angles to find the corresponding parts.

AB YX

BC ZY

CA XZ

A X

B Y

C Z

ABC ZYX

Pg. 256

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Suppose Suppose JKL JKL PQR. List PQR. List all pairs of sides and angles all pairs of sides and angles that must be congruent.that must be congruent.

JK KL JL J K

L

PQ

RQPPRQR Letters

MUST be in the correct

order!

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Write a congruence statement for Write a congruence statement for these triangles.these triangles.

MNO TUS

Try It:

Pg. 257

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A correspondence between A correspondence between two geometric figures is any two geometric figures is any way of pairing up their way of pairing up their vertices. A vertices. A congruence congruence correspondence correspondence matches the matches the vertices so that all pairs of vertices so that all pairs of corresponding parts are corresponding parts are congruent.congruent.

Pg. 257

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The symbol for “corresponds to” is The symbol for “corresponds to” is . . For example For example ABC ABC ZYX. ZYX.

The order of the letters in the The order of the letters in the statement specifies the corresponding statement specifies the corresponding

sides and angles.sides and angles.Pg. 257

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Definition:Definition:

Two triangles are congruent triangles if and only if all of their corresponding parts are congruent.

Congruent triangles Non-Congruent triangles

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#1

Pg. 258

Give a congruence correspondence for each figure. Use the figure to write the congruence.

DEF XZY

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#2

Pg. 258

Give a congruence correspondence for each figure. Use the figure to write the congruence.

GHI NPM

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Draw XYZ and UVW so that XYZ UVW. Mark the congruent parts. List the pairs of corresponding

congruent parts.

#3

Pg. 258

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Draw and mark triangles for the congruenceJKL MNP.

Rewrite the congruence in 5 other ways.

#4

Pg. 258

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Write congruence statements for the triangles in the figure that appear to be congruent.

#8

Pg. 258

TXW VYU TYU VXWTWV VUT

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#9 -12

Pg. 259

In the figure, ABC EDC. Find each measure.

9. mD = 10. CE =

11. MDCE = 12. BC =

80o

65o

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8

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#13 -16

Pg. 259

In the figure, TUV WZY. Find each measure.

13. YZ = 14. WY =

15. VT = 16. TU =

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3

3

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Homework: Practice 4-2AHomework: Practice 4-2A

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