Identify line and rotational symmetries in 2 & 3-dimensioanl figures. Geometry Lesson: 9 – 5 Symmetry Objective: Identify line and rotational symmetries in 2 & 3-dimensioanl figures.

Symmetry A figure is symmetric if a rigid motion – reflection, translation, rotation, or glide reflection – maps the figure onto itself. Line symmetry

State whether the object appears to have line symmetry. Write yes or no. If so, draw all lines of symmetry, and state their number. 1 line of symmetry

State whether the object appears to have line symmetry. Write yes or no. If so, draw all lines of symmetry, and state their number. 5 lines of symmetry

No lines of symmetry It’s an oyster… State whether the object appears to have line symmetry. Write yes or no. If so, draw all lines of symmetry, and state their number. It’s an oyster… No lines of symmetry

Rotational Symmetry

Magnitude of symmetry (or angle of rotation) Order of symmetry The number of times a figure maps onto itself. Magnitude of symmetry (or angle of rotation) The smallest angle through which a figure can be rotated so that it maps Magnitude = 360 / order

Can turn it 6 times to lay back on itself. State whether the figure has rotational symmetry. Write yes or no. If so, locate the center of symmetry, and state the order and magnitude of symmetry. Can turn it 6 times to lay back on itself.

No rotational symmetry. State whether the figure has rotational symmetry. Write yes or no. If so, locate the center of symmetry, and state the order and magnitude of symmetry. No rotational symmetry.

Can turn it 2 times to lay back on itself. State whether the figure has rotational symmetry. Write yes or no. If so, locate the center of symmetry, and state the order and magnitude of symmetry. Can turn it 2 times to lay back on itself.

Can turn it 5 times to lay back on itself. State whether the figure has rotational symmetry. Write yes or no. If so, locate the center of symmetry, and state the order and magnitude of symmetry. Can turn it 5 times to lay back on itself.

Can turn it 3 times to lay back on itself. State whether the figure has rotational symmetry. Write yes or no. If so, locate the center of symmetry, and state the order and magnitude of symmetry. Can turn it 3 times to lay back on itself.

Can turn it 8 times to lay back on itself. State whether the figure has rotational symmetry. Write yes or no. If so, locate the center of symmetry, and state the order and magnitude of symmetry. Can turn it 8 times to lay back on itself.

Plane symmetry Has also plane symmetry

State whether the figure has plane symmetry, axis symmetry, both, or neither.

Both Neither Plane Both State whether each piece of sports equipment appears to have symmetry, axis symmetry, both, or neither (ignore stitching or markings). Both Neither Plane Both

Draw dilations in the coordinate plane. Geometry Lesson: 9 – 6 Dilation Objective: Draw dilations in the coordinate plane.

Draw a dilation Use the book’s example Will be extra credit if accurate.

Dilation Enlargement Reduction Dilation is bigger than original figure. Scale factor is bigger than 1 Reduction Dilation is smaller than original figure. Scale factor is smaller than 1

Dilations in the coordinate plane

Homework Worksheet Pg. 32 & 33 Worksheet Pg. 38 & 39