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Page 1 1. Give the order of rotational symmetry for each of the following figures when rotated about the marked point (x): Solution: (i) A figure is said to have rotational symmetry if its fits onto itself more than once during a full turn that is rotation through 360 o Therefore the given figure has its rotational symmetry as 4. (ii) A figure is said to have rotational symmetry if its fits onto itself more than once during a full turn that is rotation through 360 o Therefore the given figure has its rotational symmetry as 3. Page 2 1. Give the order of rotational symmetry for each of the following figures when rotated about the marked point (x): Solution: (i) A figure is said to have rotational symmetry if its fits onto itself more than once during a full turn that is rotation through 360 o Therefore the given figure has its rotational symmetry as 4. (ii) A figure is said to have rotational symmetry if its fits onto itself more than once during a full turn that is rotation through 360 o Therefore the given figure has its rotational symmetry as 3. (iii) A figure is said to have rotational symmetry if its fits onto itself more than once during a full turn that is rotation through 360 o Therefore the given figure has its rotational symmetry as 3. (iv) A figure is said to have rotational symmetry if its fits onto itself more than once during a full turn that is rotation through 360 o Therefore the given figure has its rotational symmetry as 4. (v) A figure is said to have rotational symmetry if its fits onto itself more than once during a full turn that is rotation through 360 o Therefore the given figure has its rotational symmetry as 2. (vi) A figure is said to have rotational symmetry if its fits onto itself more than once during a full turn that is rotation through 360 o Therefore the given figure has its rotational symmetry as 4. (vii) A figure is said to have rotational symmetry if its fits onto itself more than once during a full turn that is rotation through 360 o Therefore the given figure has its rotational symmetry as 5. (viii) A figure is said to have rotational symmetry if its fits onto itself more than once during a full turn that is rotation through 360 o Therefore the given figure has its rotational symmetry as 6. (ix) A figure is said to have rotational symmetry if its fits onto itself more than once during a full turn that is rotation through 360 o Therefore the given figure has its rotational symmetry as 3. 2. Name any two figures that have both line symmetry and rotational symmetry. Solution: An equilateral triangle and a square have both lines of symmetry and rotational symmetry. Page 3 1. Give the order of rotational symmetry for each of the following figures when rotated about the marked point (x): Solution: (i) A figure is said to have rotational symmetry if its fits onto itself more than once during a full turn that is rotation through 360 o Therefore the given figure has its rotational symmetry as 4. (ii) A figure is said to have rotational symmetry if its fits onto itself more than once during a full turn that is rotation through 360 o Therefore the given figure has its rotational symmetry as 3. (iii) A figure is said to have rotational symmetry if its fits onto itself more than once during a full turn that is rotation through 360 o Therefore the given figure has its rotational symmetry as 3. (iv) A figure is said to have rotational symmetry if its fits onto itself more than once during a full turn that is rotation through 360 o Therefore the given figure has its rotational symmetry as 4. (v) A figure is said to have rotational symmetry if its fits onto itself more than once during a full turn that is rotation through 360 o Therefore the given figure has its rotational symmetry as 2. (vi) A figure is said to have rotational symmetry if its fits onto itself more than once during a full turn that is rotation through 360 o Therefore the given figure has its rotational symmetry as 4. (vii) A figure is said to have rotational symmetry if its fits onto itself more than once during a full turn that is rotation through 360 o Therefore the given figure has its rotational symmetry as 5. (viii) A figure is said to have rotational symmetry if its fits onto itself more than once during a full turn that is rotation through 360 o Therefore the given figure has its rotational symmetry as 6. (ix) A figure is said to have rotational symmetry if its fits onto itself more than once during a full turn that is rotation through 360 o Therefore the given figure has its rotational symmetry as 3. 2. Name any two figures that have both line symmetry and rotational symmetry. Solution: An equilateral triangle and a square have both lines of symmetry and rotational symmetry. 3. Give an example of a figure that has a line of symmetry but does not have rotational symmetry. Solution: A semicircle and an isosceles triangle have a line of symmetry but do not have rotational symmetry. 4. Give an example of a geometrical figure which has neither a line of symmetry nor a rotational symmetry. Solution: A scalene triangle has neither a line of symmetry nor a rotational symmetry. Page 4 1. Give the order of rotational symmetry for each of the following figures when rotated about the marked point (x): Solution: (i) A figure is said to have rotational symmetry if its fits onto itself more than once during a full turn that is rotation through 360 o Therefore the given figure has its rotational symmetry as 4. (ii) A figure is said to have rotational symmetry if its fits onto itself more than once during a full turn that is rotation through 360 o Therefore the given figure has its rotational symmetry as 3. (iii) A figure is said to have rotational symmetry if its fits onto itself more than once during a full turn that is rotation through 360 o Therefore the given figure has its rotational symmetry as 3. (iv) A figure is said to have rotational symmetry if its fits onto itself more than once during a full turn that is rotation through 360 o Therefore the given figure has its rotational symmetry as 4. (v) A figure is said to have rotational symmetry if its fits onto itself more than once during a full turn that is rotation through 360 o Therefore the given figure has its rotational symmetry as 2. (vi) A figure is said to have rotational symmetry if its fits onto itself more than once during a full turn that is rotation through 360 o Therefore the given figure has its rotational symmetry as 4. (vii) A figure is said to have rotational symmetry if its fits onto itself more than once during a full turn that is rotation through 360 o Therefore the given figure has its rotational symmetry as 5. (viii) A figure is said to have rotational symmetry if its fits onto itself more than once during a full turn that is rotation through 360 o Therefore the given figure has its rotational symmetry as 6. (ix) A figure is said to have rotational symmetry if its fits onto itself more than once during a full turn that is rotation through 360 o Therefore the given figure has its rotational symmetry as 3. 2. Name any two figures that have both line symmetry and rotational symmetry. Solution: An equilateral triangle and a square have both lines of symmetry and rotational symmetry. 3. Give an example of a figure that has a line of symmetry but does not have rotational symmetry. Solution: A semicircle and an isosceles triangle have a line of symmetry but do not have rotational symmetry. 4. Give an example of a geometrical figure which has neither a line of symmetry nor a rotational symmetry. Solution: A scalene triangle has neither a line of symmetry nor a rotational symmetry. 5. Give an example of a letter of the English alphabet which has (i) No line of symmetry (ii) Rotational symmetry of order 2. Solution: (i) The letter of the English alphabet which has no line of symmetry is Z. (ii) The letter of the English alphabet which has rotational symmetry of order 2 is N. 6. What is the line of symmetry of a semi-circle? Does it have rotational symmetry? Solution: A semicircle (half of a circle) has only one line of symmetry. In the figure, there is one line of symmetry. The figure is symmetric along the perpendicular bisector I of the diameter XY. A semi-circle does not have any rotational symmetry. 7. Draw, whenever possible, a rough sketch of (i) a triangle with both line and rotational symmetries. (ii) a triangle with only line symmetry and no rotational symmetry. (iii) a quadrilateral with a rotational symmetry but not a line of symmetry. (iv) a quadrilateral with line symmetry but not a rotational symmetry. Page 5 1. Give the order of rotational symmetry for each of the following figures when rotated about the marked point (x): Solution: (i) A figure is said to have rotational symmetry if its fits onto itself more than once during a full turn that is rotation through 360 o Therefore the given figure has its rotational symmetry as 4. (ii) A figure is said to have rotational symmetry if its fits onto itself more than once during a full turn that is rotation through 360 o Therefore the given figure has its rotational symmetry as 3. (iii) A figure is said to have rotational symmetry if its fits onto itself more than once during a full turn that is rotation through 360 o Therefore the given figure has its rotational symmetry as 3. (iv) A figure is said to have rotational symmetry if its fits onto itself more than once during a full turn that is rotation through 360 o Therefore the given figure has its rotational symmetry as 4. (v) A figure is said to have rotational symmetry if its fits onto itself more than once during a full turn that is rotation through 360 o Therefore the given figure has its rotational symmetry as 2. (vi) A figure is said to have rotational symmetry if its fits onto itself more than once during a full turn that is rotation through 360 o Therefore the given figure has its rotational symmetry as 4. (vii) A figure is said to have rotational symmetry if its fits onto itself more than once during a full turn that is rotation through 360 o Therefore the given figure has its rotational symmetry as 5. (viii) A figure is said to have rotational symmetry if its fits onto itself more than once during a full turn that is rotation through 360 o Therefore the given figure has its rotational symmetry as 6. (ix) A figure is said to have rotational symmetry if its fits onto itself more than once during a full turn that is rotation through 360 o Therefore the given figure has its rotational symmetry as 3. 2. Name any two figures that have both line symmetry and rotational symmetry. Solution: An equilateral triangle and a square have both lines of symmetry and rotational symmetry. 3. Give an example of a figure that has a line of symmetry but does not have rotational symmetry. Solution: A semicircle and an isosceles triangle have a line of symmetry but do not have rotational symmetry. 4. Give an example of a geometrical figure which has neither a line of symmetry nor a rotational symmetry. Solution: A scalene triangle has neither a line of symmetry nor a rotational symmetry. 5. Give an example of a letter of the English alphabet which has (i) No line of symmetry (ii) Rotational symmetry of order 2. Solution: (i) The letter of the English alphabet which has no line of symmetry is Z. (ii) The letter of the English alphabet which has rotational symmetry of order 2 is N. 6. What is the line of symmetry of a semi-circle? Does it have rotational symmetry? Solution: A semicircle (half of a circle) has only one line of symmetry. In the figure, there is one line of symmetry. The figure is symmetric along the perpendicular bisector I of the diameter XY. A semi-circle does not have any rotational symmetry. 7. Draw, whenever possible, a rough sketch of (i) a triangle with both line and rotational symmetries. (ii) a triangle with only line symmetry and no rotational symmetry. (iii) a quadrilateral with a rotational symmetry but not a line of symmetry. (iv) a quadrilateral with line symmetry but not a rotational symmetry. Solution: (i) An equilateral triangle has 3 lines of symmetry and a rotational symmetry of order 3. (ii) An isosceles triangle has only 1 line of symmetry and no rotational symmetry. (iii) A parallelogram is a quadrilateral which has no line of symmetry but a rotational symmetry of order 2.Read More
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