對稱

• 反射對稱：reflection symmetry，又稱為鏡對稱 (mirror symmetry)。 包括線對稱 (line symmetry)、點對稱 (point symmetry)、面對稱 (plane symmetry)。
• 旋轉對稱：rotation symmetry。
• 平移對稱：translation symmetry。
• 滑動反射，平移與反射的合成，不在課程裡。

Isosceles triangles are symmetric figures.

The bisector of the vertex angle of an isosceles triangle is a line of symmetry / symmetry line for the triangle.

Any line through its center is an axis of symmetry for the circle.

Points $$A$$ and $$A^\prime$$ are symmetric with respect to / about / across the line $$L$$.

$$A^\prime$$ is the reflection of $$A$$ across line $$L$$.
$$A^\prime$$ is the symmetrical point of $$A$$ from the line $$L$$.

 [語音講解：symmetry.mp3]

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Created: Mar 24, 2022
Last Revised: 08/20, 11/04