Ch 12 extends symmetry concepts from Class 6 to include rotational symmetry — where a shape looks the same after being rotated by an angle less than 360°. Students explore both line and rotational symmetry in regular polygons and everyday objects.
A figure has line symmetry if a line divides it into two mirror-image halves. Regular polygons with n sides have n lines of symmetry.
A figure has rotational symmetry if it looks exactly the same after rotation by an angle less than 360°. The order of rotational symmetry is how many times the figure coincides with itself in a full 360° rotation. A square has order 4 (matches at 90°, 180°, 270°, 360°).
Download: https://ncert.nic.in/textbook/pdf/gemh112.pdf | Complete book: https://ncert.nic.in/textbook/pdf/gemh1ps.zip
Yes. The letter S and a parallelogram (non-rectangle) have rotational symmetry of order 2 but no line of symmetry.
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