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9-2 Reflections

9-2 Reflections. Key Concepts:. R stands for reflection and the Subscript tells you what to reflect on (ex: R x-axis) The “line of reflection” is what you reflect on Reflection: keeps size and shape, it’s always a RIGID MOTION or ISOMETRY!!. Just watch! Don’t need to write.

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9-2 Reflections

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  1. 9-2 Reflections

  2. Key Concepts: • R stands for reflection and the Subscript tells you what to reflect on (ex: Rx-axis) • The “line of reflection” is what you reflect on • Reflection: keeps size and shape,it’s always a RIGID MOTION or ISOMETRY!!

  3. Just watch! Don’t need to write. • Rk = reflect over line k • Rl = reflect over line l l k

  4. Rx-axis Ry-axis Ry = x Ry =-x Example Original: (3,4) • (3,-4) • (-3,4) • (4,3) • (-4, -3)

  5. TOO • Graph each original • Find and graph the reflection across: • x-axis • y-axis • y = x • y = -x 1) (-2,-3) 2) (4,1) Answers: 1) (-2,3) (2,-3) (-3,-2) (3, 2) 2) (4,-1) (-4,1) (1,4) (-1, -4)

  6. Rules • Look at the answers that you got for the example and the 2 TOO. • Write mappings for reflecting across: • x-axis (x stays the same!) • y-axis (y stays the same!) • y = x (they flip flop, signs STAY) • y = -x (flip flop, signs CHANGE) But what about other lines????? • (x,y) → (x,-y) • (x,y)→ (-x,y) • (x,y)→ (y,x) • (x,y)→ (-y, -x)

  7. Point P has coordinates (3,4). What are the coordinates of:

  8. Reflections of Triangles

  9. Reflections over 2 lines:Find the image of Z(1, 1) after two reflections, first across line ℓ1, and then across line ℓ2. • ℓ1 : x = 2, ℓ2 : y-axis

  10. Homework • WS from: Pg. 557 # 7-14, 28-29, 32-34, 37

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