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Think About This: Tuesday, January 31,2012

Think About This: Tuesday, January 31,2012. Partner Answers! . Are points E and C collinear? What is the intersection of plane ADCB and plane HGCD? Name the 4 th point in plane EHC. P. 33: 87-94. Solutions to Page 33. 87)never 88) never 89)always 90)never 91)always 92)always

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Think About This: Tuesday, January 31,2012

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  1. Think About This:Tuesday, January 31,2012 Partner Answers!  • Are points E and C collinear? • What is the intersection of plane ADCB and plane HGCD? • Name the 4th point in plane EHC. • P. 33: 87-94

  2. Solutions to Page 33 • 87)never • 88) never • 89)always • 90)never • 91)always • 92)always • 93)always • 94)never

  3. a b Parallel lines are coplanar lines that do not intersect. • These symbols indicate lines a and b are parallel. a || b

  4. Skew lines are noncoplanar; therefore, they are not parallel and do not intersect. AB || EF AB and CG are skew.

  5. Parallel planes are planes that do not intersect. Plane ABCD || Plane GHIJ

  6. Today’s Goals…

  7. 2 cm 2 cm A B C D Two segments with the same length are congruent () segments. If AB = CD, then AB  CD

  8. A B C D E A B C Stop and Think…AB + BC = 6 and AC = 6. Segment Addition PostulateIf three points A, B, and C are collinear and B is between A and C, then AB + BC = AC.

  9. 2x – 8 3x – 12 D S T Ex.1:If DT = 60, find the value of x. Then find DS and ST. DS + ST = DT(Segment Addition Postulate)

  10. 4x – 20 2x + 30 E F G You Try… #1 • EG = 100. Find the value of x. • Then find EF and FG.

  11. A B C AB  BC Midpoint • A midpoint of a segment is a point that divides a segment into two congruent segments.

  12. 2x + 1 3x – 4 A C B Ex.2:C is the midpoint of AB. Find AC, CB, and AB. AC = CB(Definition of midpoint)

  13. You Try… #2 • Z is the midpoint of XY, and XY = 27. • Find XZ.

  14. Angle () • Formed by two rays with the same endpoint. • The endpoint is the vertex of the angle.

  15. 55 90 135 180 Classifying Angles Acute is between 0 and 90. Right is equal to 90. Obtuse is between 90 and 180. Straight is equal to 180.

  16. B A O C Angle Addition PostulatePART I: • If point B is in the interior of AOC, then mAOB + mBOC = mAOC.

  17. B A O C Angle Addition PostulatePART II: • If AOC is a straight angle, then: mAOB + mBOC = 180.

  18. Ex.3a:What is mTSW ifmRST = 50 and mRSW = 125?

  19. G D E F Ex.3b: If mDEG = 145, find mGEF.

  20. A B 1 2 C You Try… #3 • Suppose that m1 = 42 and mABC = 88. • Find m2.

  21. 55 55 Congruent AnglesAngles with the same measure • If m1 = m2, then 1  2.

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