Lesson · Grade 6 · Mathematics
Reflections: Same Distance, Other Side of the Mirror
- Grade 6
- Mathematics
- 1 min 4 s
- British Columbia
- BC6-MA-40
A triangle on a square grid is reflected in a vertical mirror line by counting each corner's distance straight across to the line (4, 1 and 3 units) and the same distance past it, with a card recording each matching pair. A copy of the triangle then folds over the line onto its image, showing that the image is the same size and shape but faces the opposite way, and the video ends on the recap that a reflection puts every point the same distance away on the other side of the mirror.
Concept: Reflections
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In one sentence
The question this lesson answers
A reflection flips a shape over a line called the mirror line.
Let us reflect triangle A B C in this mirror line.
Transcript
What the lesson says
A reflection flips a shape over a line called the mirror line.
Let us reflect triangle A B C in this mirror line.
Corner A is 4 units from the mirror line, counting straight across.
Count the same 4 units on the other side to find A prime.
B is 1 unit from the mirror, so B prime is 1 unit past it.
C is 3 units from the mirror, so C prime is 3 units past it.
Join A prime, B prime and C prime to draw the image.
Fold along the mirror line, and the triangle lands exactly on its image.
The image is the same size and shape, but it faces the opposite way.
Each corner moved straight across, at a right angle to the mirror.
A reflection puts every point the same distance away, on the other side of the mirror line.
Curriculum
Where this fits
- British Columbia, Grade 6
Mathematics, Geometry and measurement: combinations of transformationsBC6-MA-40
Previous: Translations: Slide Every Point the Same WayNext: Rotations: Turning a Shape About a Point
- British Columbia, Grade 7
Mathematics, Geometry and measurement: combinations of transformationsBC7-MA-60
Previous: Translations: Slide Every Point the Same WayNext: Rotations: Turning a Shape About a Point
This lesson is also listed in Grade 7.
The outcomes and strands follow the British Columbia curriculum.
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