Page 227 - Start Up Mathematics_7

Example 8: Complete the table:

Angle of
Shape Centre of rotation Order of rotation
rotation

Square

Rectangle

Rhombus

Equilateral
Triangle

Regular
Hexagon

Circle

Semicircle

Solution: Order of Angle of
Shape Centre of rotation
rotation rotation
Square Point of intersection of diagonals 4 90°
Rectangle Point of intersection of diagonals 2 180°
Rhombus Point of intersection of diagonals 2 180°
Equilateral Point of intersection of medians
Triangle 3 120°
Regular Point of intersection of diagonals 60°
Hexagon joining the opposite vertices 6
Circle Centre of circle Infinite Any angle
Semicircle Midpoint of diameter 1 360°

Maths Lab Activity

Objective: To find the rotational symmetry of a parallelogram
Step 1: Draw a parallelogram on a white sheet of paper.

Step 2: Draw an identical parallelogram on a tracing paper. Obtain a cutout of the parallelogram
from the tracing paper and place it on the parallelogram drawn on the white sheet.
Step 3: Put a pin at O, the point of intersection of the diagonals. Before putting the pin
ensure the cutout of the parallelogram coincide with the one drawn on the white
sheet. Put an arrow mark on the diagonal near the vertex.

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