Unit 8, Lesson 5
Symmetry in Figures (Part 2)
Grade 4
Activity 1
Each shaded triangle is half of a whole figure that has a line of symmetry shown by the dashed line.
Clare drew some segments to show the missing half of each figure.
2 shapes on grid. Left grid has two triangles, one shaded, one not, sharing a vertical side that is overlapped by a dashed line. Right grid has two triangles, one shaded, one not, sharing a horizontal side that is overlapped by a dashed line. On both grids, the triangles are the same size and shape, but not mirrored across the dashed line.
Do you agree that the dashed line is a line of symmetry for each figure Clare completed? Explain your reasoning. If you disagree with Clare's work, show a way to complete the drawing so the dashed line is a line of symmetry.
Activity 2
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Here are 3 figures. Each figure is half of a whole figure. The dashed line is a line symmetry of that whole figure.
3 shapes. Triangle with a horizontal side overlapping a dashed line. Trapezoid with horizontal side overlapping a dash line. Rhombus with diagonal side overlapping a dash line.Use patty paper to help you draw the whole figure.
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Each figure on the grid is half of a whole figure. The dashed line shows the line of symmetry for the whole figure. Use the grid to help you draw the whole figure. Be as precise as possible.
3 shapes on grid. Triangle with vertical side overlapping dashed line. Trapezoid with horizontal side overlapping dashed line. Half a star shape with vertical side overlapping dashed line. -
Here is another figure that is half of a whole figure with a vertical line of symmetry. Draw the whole figure. Be as precise as possible.
Student Section Summary
We looked at different attributes of shapes, such as the number and length of sides, the measurements of sides and angles, and whether the shapes had parallel or perpendicular sides.
We then used these attributes to classify quadrilaterals and triangles.
Right triangles have 1 right angle.
Parallelograms have 2 pairs of parallel sides.
Rectangles have 2 pairs of parallel sides and 4 right angles.
Rhombuses have 4 equal sides.
Squares have 4 equal sides and 4 right angles.
We also learned about symmetry. A figure has symmetry if its parts can match up exactly after it is folded or turned. A figure that has a line of symmetry can be folded along that line to create 2 halves that match up exactly.