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6-2. Properties of Parallelograms. Warm Up. Lesson Presentation. Lesson Quiz. Holt Geometry. 6.2 Properties of Parallelograms. Warm Up Find the value of each variable. 1. x 2. y 3. z. 2. 18. 4. 6.2 Properties of Parallelograms. Objectives.

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6-2

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  1. 6-2 Properties of Parallelograms Warm Up Lesson Presentation Lesson Quiz Holt Geometry

  2. 6.2 Properties of Parallelograms Warm Up Find the value of each variable. 1.x2.y 3.z 2 18 4

  3. 6.2 Properties of Parallelograms Objectives Prove and apply properties of parallelograms. Use properties of parallelograms to solve problems.

  4. 6.2 Properties of Parallelograms Vocabulary parallelogram

  5. 6.2 Properties of Parallelograms Any polygon with four sides is a quadrilateral. However, some quadrilaterals have special properties. These special quadrilaterals are given their own names.

  6. 6.2 Properties of Parallelograms Helpful Hint Opposite sides of a quadrilateral do not share a vertex. Opposite angles do not share a side.

  7. 6.2 Properties of Parallelograms A quadrilateral with two pairs of parallel sides is a parallelogram. To write the name of a parallelogram, you use the symbol .

  8. 6.2 Properties of Parallelograms

  9. 6.2 Properties of Parallelograms

  10. 6.2 Properties of Parallelograms In CDEF, DE = 74 mm, DG = 31 mm, and mFCD = 42°. Find CF. opp. sides Example 1A: Properties of Parallelograms CF = DE Def. of segs. CF = 74 mm Substitute 74 for DE.

  11. 6.2 Properties of Parallelograms In CDEF, DE = 74 mm, DG = 31 mm, and mFCD = 42°. Find mEFC. cons. s supp. Example 1B: Properties of Parallelograms mEFC + mFCD = 180° mEFC + 42= 180 Substitute 42 for mFCD. mEFC = 138° Subtract 42 from both sides.

  12. 6.2 Properties of Parallelograms In CDEF, DE = 74 mm, DG = 31 mm, and mFCD = 42°. Find DF. diags. bisect each other. Example 1C: Properties of Parallelograms DF = 2DG DF = 2(31) Substitute 31 for DG. DF = 62 Simplify.

  13. 6.2 Properties of Parallelograms opp. sides Check It Out! Example 1a In KLMN, LM = 28 in., LN = 26 in., and mLKN = 74°. Find KN. LM = KN Def. of segs. LM = 28 in. Substitute 28 for DE.

  14. 6.2 Properties of Parallelograms opp. s  Check It Out! Example 1b In KLMN, LM = 28 in., LN = 26 in., and mLKN = 74°. Find mNML. NML  LKN mNML = mLKN Def. of  s. mNML = 74° Substitute 74° for mLKN. Def. of angles.

  15. 6.2 Properties of Parallelograms diags. bisect each other. Check It Out! Example 1c In KLMN, LM = 28 in., LN = 26 in., and mLKN = 74°. Find LO. LN = 2LO 26 = 2LO Substitute 26 for LN. LO = 13 in. Simplify.

  16. 6.2 Properties of Parallelograms opp. s  Example 2A: Using Properties of Parallelograms to Find Measures WXYZ is a parallelogram. Find YZ. YZ = XW Def. of  segs. 8a – 4 = 6a + 10 Substitute the given values. Subtract 6a from both sides and add 4 to both sides. 2a = 14 a = 7 Divide both sides by 2. YZ = 8a – 4 = 8(7) – 4 = 52

  17. 6.2 Properties of Parallelograms cons. s supp. Example 2B: Using Properties of Parallelograms to Find Measures WXYZ is a parallelogram. Find mZ. mZ + mW = 180° (9b + 2)+ (18b –11) = 180 Substitute the given values. Combine like terms. 27b – 9 = 180 27b = 189 b = 7 Divide by 27. mZ = (9b + 2)° = [9(7) + 2]° = 65°

  18. 6.2 Properties of Parallelograms diags. bisect each other. Check It Out! Example 2a EFGH is a parallelogram. Find JG. EJ = JG Def. of  segs. 3w = w + 8 Substitute. 2w = 8 Simplify. w = 4 Divide both sides by 2. JG = w + 8 = 4 + 8 = 12

  19. 6.2 Properties of Parallelograms diags. bisect each other. Check It Out! Example 2b EFGH is a parallelogram. Find FH. FJ = JH Def. of  segs. 4z – 9 = 2z Substitute. 2z = 9 Simplify. z = 4.5 Divide both sides by 2. FH = (4z – 9) + (2z) = 4(4.5) – 9 + 2(4.5) = 18

  20. 6.2 Properties of Parallelograms Remember! When you are drawing a figure in the coordinate plane, the name ABCD gives the order of the vertices.

  21. 6.2 Properties of Parallelograms Example 4A: Using Properties of Parallelograms in a Proof Write a two-column proof. Given: ABCD is a parallelogram. Prove:∆AEB∆CED

  22. 6.2 Properties of Parallelograms 3. diags. bisect each other 2. opp. sides  Example 4A Continued Proof: 1. ABCD is a parallelogram 1. Given 4. SSS Steps 2, 3

  23. 6.2 Properties of Parallelograms Example 4B: Using Properties of Parallelograms in a Proof Write a two-column proof. Given: GHJN and JKLM are parallelograms. H and M are collinear. N and K are collinear. Prove:H M

  24. 6.2 Properties of Parallelograms 2.H and HJN are supp. M and MJK are supp. 2. cons. s supp. Example 4B Continued Proof: 1.GHJN and JKLM are parallelograms. 1. Given 3.HJN  MJK 3. Vert. s Thm. 4.H  M 4. Supps. Thm.

  25. 6.2 Properties of Parallelograms Check It Out! Example 4 Write a two-column proof. Given: GHJN and JKLM are parallelograms. H and M are collinear. N and K are collinear. Prove: N  K

  26. 6.2 Properties of Parallelograms 2.N and HJN are supp. K and MJK are supp. 2. cons. s supp. Check It Out! Example 4 Continued Proof: 1.GHJN and JKLM are parallelograms. 1. Given 3.HJN  MJK 3. Vert. s Thm. 4.N  K 4. Supps. Thm.

  27. 6.2 Properties of Parallelograms Lesson Quiz: Part I In PNWL, NW = 12, PM = 9, and mWLP = 144°. Find each measure. 1.PW2. mPNW 18 144°

  28. 6.2 Properties of Parallelograms Lesson Quiz: Part II QRST is a parallelogram. Find each measure. 2.TQ3. mT 71° 28

  29. 6.2 Properties of Parallelograms 1.RSTU is a parallelogram. 1. Given 3.R  T 4. ∆RSU∆TUS 4. SAS 2. cons. s  3. opp. s  Lesson Quiz: Part III 6. Write a two-column proof. Given:RSTU is a parallelogram. Prove: ∆RSU∆TUS

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