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Transformations

边玩边学

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给教育者: 面向 Transformations(Mathematics,Geometry and measures)的即用型课程幻灯片, 复习笔记——用在你的课堂上,或将该知识点作为学习者可实时游玩的互动课堂活动来运行。

课程笔记

Translation

  • A translation slides every point by the same vector \begin{pmatrix} a \\ b \end{pmatrix}: a units right (left if negative) and b units up (down if negative).
  • The shape stays the same size and orientation.

Translation by (3, 1)

Translation by (3, 1)xy-5-4-3-2-112345-5-4-3-2-112345AA′BB′CC′Translation vector (3, 1)

Reflection

  • A reflection flips a shape in a mirror line such as x = 2, y = 0 or y = x. Each point is the same distance from the mirror on the opposite side.
  • Describe it by giving the equation of the mirror line.

Reflection in x = 0

Reflection in x = 0xy-5-4-3-2-112345-5-4-3-2-112345AA′BB′CC′Mirror line: x = 0 (y-axis)

Rotation

  • A rotation turns a shape about a centre. Give centre, angle and direction, except that a 180° rotation does not need direction.
  • A 180° rotation gives the same result in either direction.

A quarter-turn about the origin

A quarter-turn about the originxy-5-4-3-2-112345-5-4-3-2-112345AA′BB′CC′Centre (0, 0) · 90° anticlockwise

Enlargement

  • For enlargement about centre C, image point P′ = C + k(P − C). Distances from C multiply by |k|.
  • A negative k places corresponding image points on the opposite side of C. For k = −½ the image is smaller, while k = −2 makes it larger. For |k| = 1 size is unchanged.

Enlargement with scale factor 2

Enlargement with scale factor 2xy-5-4-3-2-112345-5-4-3-2-112345AA′BB′CC′Centre (0, 0) · scale factor 2

Combining and describing

  • Translation, reflection and rotation give congruent images. Enlargement with nonzero k gives a similar image and is also congruent when |k| = 1.
  • Give the translation vector, reflection line, rotation centre and angle with direction where needed, or enlargement centre and scale factor.

幻灯片

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练习题

免费预览——31 题中的 8 题。注册即可查看全部。
  1. 1.Which transformation slides a shape without turning it?

    Easy
    • Arotation
    • Breflection
    • Ctranslation
    • Denlargement
  2. 2.What is the image of (2, 3) after translation by \begin{pmatrix} 4 \\ 1 \end{pmatrix}?

    Easy
    • A(6, 4)
    • B(-2, 2)
    • C(8, 3)
    • D(5, 7)
  3. 3.What is the image of (2, 3) after reflection in the x-axis?

    Easy
    • A(2, -3)
    • B(-2, 3)
    • C(-2, -3)
    • D(3, 2)
  4. 4.What is the image of (2, 3) after reflection in the y-axis?

    Easy
    • A(2, -3)
    • B(-2, 3)
    • C(-2, -3)
    • D(3, 2)
  5. 5.What is the image of (2, 3) after reflection in y = x?

    Easy
    • A(3, 2)
    • B(-3, -2)
    • C(2, -3)
    • D(-2, 3)
  6. 6.What is the image of (2, 3) after a rotation of 180° about the origin?

    Easy
    • A(-2, -3)
    • B(2, -3)
    • C(3, 2)
    • D(-3, 2)
  7. 7.What is the image of (2, 0) after a 90° anticlockwise rotation about the origin?

    Easy
    • A(0, 2)
    • B(0, -2)
    • C(-2, 0)
    • D(2, 2)
  8. 8.A shape is enlarged by scale factor 3. A side was 4 cm. What is the new side?

    Easy
    • A7 cm
    • B12 cm
    • C1.33 cm
    • D81 cm

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