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Congruence and Similarity

Congruence and Similarity. Form 1 Mathematics Chapter 11. Reminder. Lesson requirement Textbook 1B Workbook 1B Notebook Before lessons start Desks in good order! No rubbish around! No toilets! Keep your folder at home Prepare for Final Exam. Reminder. Missing HW Detention SHW (I)

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Congruence and Similarity

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  1. Congruenceand Similarity Form 1 Mathematics Chapter 11

  2. Reminder • Lesson requirement • Textbook 1B • Workbook 1B • Notebook • Before lessons start • Desks in good order! • No rubbish around! • No toilets! • Keep your folder at home • Prepare for Final Exam

  3. Reminder • Missing HW • Detention • SHW (I) • 8th May (Wednesday) • SHW (II) • 14th May (Tuesday) • OBQ • 15th May (Wednesday) • CBQ • 20th May (Monday)

  4. X Y Congruence (全等,p.172) • Congruent figures (全等圖形) 1. Figures having the same shape and size are called congruent figures. e.g. Figures X and Y below are congruent figures. 2.Two congruent figures can fit exactly on each other.

  5. Time for Practice • Page 173 of Textbook 1B • Class Practice • Pages 176 – 177 of Textbook 1B • Questions 1 – 2 • Page 73 of Workbook 1B • Question 1

  6. Transformation and Congruence (p.174) • We learnt transformations in Chapter 9: • Translation • Reflection • Rotation • Enlargement and Reduction • Which one will NOT change the shape? • Try Class Discussion on p.174

  7. Transformation and Congruence (p.174) 1.When a figure is translated, rotated or reflected, the image produced is congruent to the original figure. 2. When a figure is reduced or enlarged, the image produced will not be congruent to the original one.

  8. A X C Z B Y Congruent Triangles(全等三角形,p.175) • Symbol “  ” means “is congruent to” When two triangles are congruent, (i)their corresponding sides (對應邊) are equal, (ii)their corresponding angles(對應角) are equal. e.g. If △ABC △XYZ, then AB = XY, BC = YZ, CA = ZX, A = X, B = Y, C = Z.

  9. Congruent Triangles (p.175) • Example 1: Name a pair of congruent triangles in the figure. From the figure above, we have △ABC  △RQP.

  10. Congruent Triangles (p.175) • Example 2: Given that △ABC  △XYZ, find the unknowns x, b and y. ∵ The corresponding sides and corresponding angles of two congruent triangles are equal, ∴ x = 5 cm, b = 6 cm, y = 50°

  11. Congruent Triangles (p.175) • Example 3: Since △PQS △RSQ, we have PQ = RS i.e. s = 8 cm and RQS = PSQ = 70° In △RSQ, 45° + RQS + r = 180° 45° + 70° + r = 180° 115° + r = 180° r = 65° Given that △PQS  △RSQ, find the unknowns s and r.

  12. Time for Practice • Page 176 of Textbook 1B • Class Practice • Pages 177 – 178 of Textbook 1B • Questions 4 – 17 • Pages 74 – 75 of Workbook 1B • Questions 2 – 5

  13. Enjoy the world of Mathematics! Ronald HUI

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