Constructions and Tilings | FIO

Question 19

Construct the following figures:

Question diagram 1Question diagram 2
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Solution
Understand the Question

Geometric constructions can be performed using a straightedge (ruler) and a compass:

  • Compass: Used to draw circles and arcs of a fixed radius, or transfer equal lengths.
  • Straightedge: Used to draw straight lines between points.
  • For figures with 6-fold rotational symmetry (like hexagons, 6-petal flowers, and 7-circle arrangements), the fundamental principle is that the side length of a regular hexagon inscribed in a circle is equal to the radius RR of the circle.

(a) Construct Figure (a): Inflexed Arc

Step 1 · Construct an Inflexed Arc

Diagram 1

  1. Draw a horizontal base line segment ABAB.
  2. Draw vertical lines upwards from AA and BB. Mark points CC on the vertical line at AA and DD on the vertical line at BB such that AC=BDAC = BD.
  3. Find the midpoint MM of segment CDCD.
  4. Draw a vertical centerline upwards through MM.
  5. Set the compass radius to CMCM.
  6. Place the compass at center CC and draw an arc curving towards the centerline.
  7. With the same radius (DM=CMDM = CM), place the compass at center DD and draw an arc curving towards the centerline.
  8. The two arcs intersect at point EE on the vertical centerline, completing the figure formed by vertical segments ACAC, BDBD and arcs CECE, DEDE.
Answer

(a) Figure (a) constructed.

(b) Construct Figure (b): Flower-like Shape

Step 1 · Construct a Flower-like Shape

Diagram 2

  1. Draw a central circle with center OO and radius RR.
  2. Mark any point AA on the circumference of the central circle.
  3. With center AA and radius RR, draw a circle passing through OO and intersecting the central circle at two points; label one point BB.
  4. With center BB and radius RR, draw another circle intersecting the central circle at a new point CC.
  5. Repeat this process around the circumference using each new intersection point as the center until 6 surrounding circles are drawn.
  6. The overlapping arcs inside the central circle form the 6 petals.
Answer

(b) Figure (b) constructed.

(c) Construct Figure (c): Hexagon inside a Circle

Step 1 · Construct a Regular Hexagon Inscribed in a Circle

Diagram 3

  1. Draw a circle with center OO and radius RR.
  2. Mark a point AA on the circumference.
  3. With center AA and compass set to radius RR, draw an arc to cut the circle at point BB.
  4. With center BB and radius RR, draw an arc to cut the circle at point CC.
  5. Continue marking points around the circumference with radius RR until 6 points (A,B,C,D,E,FA, B, C, D, E, F) are marked.
  6. Connect consecutive vertices with straight lines (AB,BC,CD,DE,EF,FAAB, BC, CD, DE, EF, FA) to form the regular hexagon.
Answer

(c) Figure (c) constructed.

(d) Construct Figure (d): Seven Circles

Step 1 · Construct Seven Intersecting Circles

Diagram 4

  1. Draw a central circle with center OO and radius RR.
  2. Choose a point AA on the circumference and draw a circle of radius RR centered at AA.
  3. Locate the intersection point BB of this circle with the central circle.
  4. Draw the next circle of radius RR centered at BB.
  5. Continue moving to each successive intersection on the central circle until all 6 surrounding circles are drawn.
  6. Keep all 7 full circles visible to complete the design.
Answer

(d) Figure (d) constructed.

(e) Construct Figure (e): Tiling Pattern

Step 1 · Construct a Hexagonal Tiling Pattern

Diagram 5

  1. Draw a circle with center OO and radius RR, and construct an inscribed regular hexagon with vertices V1,V2,V3,V4,V5,V6V_1, V_2, V_3, V_4, V_5, V_6.
  2. Draw segments from center OO to each vertex V1,V2,,V6V_1, V_2, \dots, V_6, dividing the hexagon into 6 large equilateral triangles (e.g., ΔOV1V2\Delta OV_1V_2).
  3. In each equilateral triangle:
    • Divide each side (OV1,OV2,V1V2OV_1, OV_2, V_1V_2) into 3 equal segments.
    • Connect corresponding division points with lines parallel to the sides of the triangle, subdividing each large triangle into 9 smaller equilateral triangles.
  4. Repeat for all 6 large equilateral triangles to reveal the complete geometric tiling pattern of stars and smaller hexagons.
Answer

(e) Figure (e) constructed.

Common Mistakes
  • Changing Compass Radius: Changing the compass opening during the step-by-step construction of hexagonal or circle patterns will prevent the arcs from closing properly back at the starting point.
  • Imprecise Midpoint / Division: In tiling patterns, dividing triangle edges unequally will cause the internal grid lines not to align parallel to the outer edges.

More questions in FIO

Q1

When constructing the perpendicular bisector, is it necessary to have the same radius for the arcs above and below XYXY? Explore this through construction, and then justify your answer.

[Hint 1: Any point that is of the same distance from XX and YY lies on the perpendicular bisector.

Hint 2: We can draw the whole line if any two of its points are known.]

Q2

Is it necessary to construct the pairs of arcs above and below XYXY? Instead, can we construct both the pairs of arcs on the same side of XYXY? Explore this through construction, and then justify your answer.

Q3

While constructing one pair of intersecting arcs, is it necessary that we use the same radii for both of them ? Explore this through construction, and then justify your answer.

Q4

Recreate this design using only a ruler and compass —

Q5

Justify why AB\text{AB} in Fig. 6.4 is the perpendicular bisector.

Q6

Can you think of different methods to construct a 9090^\circ angle at a given point on a line using a rope?

Q7

Construct at least 4 different angles. Draw their bisectors.

Q8

Construct the 8-petalled figure shown in Fig. 6.5.

Q9

In Step 2 of angle bisection, if arcs of equal radius are drawn on the other side, as shown in the figure, will the line OCOC still be an angle bisector? Explore this through construction, and then justify your answer.

Q10

What are the other angles that can be constructed using angle bisection? Can you construct 65.565.5^\circ angle?

Q11

Come up with a method to construct the angle bisector using a rope.

Q12

Construct the following figure.

How do we construct the petals so that they are of the maximum possible size within a given square?

Q13

Construct at least 4 different angles in different orientations without taking any measurement. Make a copy of all these angles.

Q14

Construct the Fig. 6.6.

Q15

Construct 4 pairs of parallel lines in different orientations.

Q16

Construct the following figure.

Q17

Use support lines in Fig. 6.11 to construct a pointed arch. Make different arches, by changing the radius of the arcs.

Q18

Make your own arch designs.

Q19

Construct the following figures:

Q20

Optical Illusion: Do you notice anything interesting about the following figure? How does this happen? Recreate this in your notebook.

Q21

Construct this figure.

[Hint: Find the angles in this figure.]

Q22

Draw a line ll and mark a point PP anywhere outside the line. Construct a perpendicular to the given line ll through PP.

[Hint: Find a line segment on ll whose perpendicular bisector passes through PP.]

Q23

How can the tangram pieces be rearranged to form each of the following figures?

Q24

Are the following tilings possible?

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