Quadrilaterals | A

Question 2

Can we complete this quadrilateral so that all its sides are of the same length?

Mark a point C whose distance from B and D is equal to AB\text{AB} (or AD\text{AD}). To do this, measure AB\text{AB} using a compass. Keeping this length as the radius, cut arcs from B and D.

Question diagram 1
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Solution
Understand the Question
  • A quadrilateral having all four sides equal in length is a rhombus (AB=BC=CD=DA\text{AB} = \text{BC} = \text{CD} = \text{DA}).
  • Given adjacent sides AB\text{AB} and AD\text{AD} with AB=AD\text{AB} = \text{AD}, we can locate the fourth vertex C\text{C} by drawing arcs of radius equal to AB\text{AB} from both B\text{B} and D\text{D}.
  • The intersection of these two arcs marks point C\text{C}, completing the quadrilateral.

Step 1 · Identify the Condition for Equal Sides

For quadrilateral ABCD\text{ABCD} to have all sides of equal length, it must satisfy: AB=BC=CD=DA\text{AB} = \text{BC} = \text{CD} = \text{DA}

A quadrilateral with four equal sides is a rhombus.Diagram 1

Step 2 · Set the Compass Radius

Measure the length of side AB\text{AB} by placing the compass needle at point A\text{A} and the pencil tip at point B\text{B}.Diagram 2

Step 3 · Locate Point C Using Arcs

Keeping the compass radius equal to AB\text{AB}:

  • Place the compass needle at B\text{B} and draw an arc.
  • Place the compass needle at D\text{D} and draw another arc intersecting the first arc.

The point of intersection is point C\text{C}.Diagram 3

Step 4 · Complete the Quadrilateral

Join point B\text{B} to C\text{C} and point D\text{D} to C\text{C} using a ruler.Diagram 4

Since AB=BC=CD=DA\text{AB} = \text{BC} = \text{CD} = \text{DA}, quadrilateral ABCD\text{ABCD} is a rhombus.

Answer

Yes, we can complete this quadrilateral so that all its sides are of the same length; the resulting figure is a rhombus.

Common Mistakes
  • Varying the Compass Radius: Changing the compass opening between cutting arcs from B\text{B} and D\text{D} will lead to unequal side lengths (BCCD\text{BC} \neq \text{CD}).
  • Assuming It Must Be a Square: A quadrilateral with all sides equal is a rhombus in general; it is only a square if the angle at vertex A\text{A} is 9090^\circ.

More questions in A

Q1

Are squares the only quadrilaterals that have equal sidelengths? Let us explore this question through construction.

Draw two equal sides ADAD and ABAB, that are not perpendicular to each other.

Q2

Can we complete this quadrilateral so that all its sides are of the same length?

Mark a point C whose distance from B and D is equal to AB\text{AB} (or AD\text{AD}). To do this, measure AB\text{AB} using a compass. Keeping this length as the radius, cut arcs from B and D.

Q3

Place two rubber bands perpendicular to each other, forming diagonals of equal length. Join the ends.

What is the quadrilateral that you get? Justify your answer.

Q4

Extend one of the diagonals on both sides by 2 cm2\text{ cm}.

What quadrilateral will you get now? Justify your answer.

Q5

Take two cardboard cutouts of an equilateral triangle of sidelength 8 cm8\text{ cm}.

  • Can you join them to get a quadrilateral?
  • What type of a quadrilateral is this? Justify your answer.
Q6

Take two cardboard cutouts of an isosceles triangle with sidelengths 8 cm8\text{ cm}, 8 cm8\text{ cm}, and 6 cm6\text{ cm}.

  • What are the different ways they can be joined to get a quadrilateral?
  • What quadrilaterals are these? Justify your answers.
Q7

Take two cardboard cutouts of a scalene triangle with sides 6 cm6\text{ cm}, 9 cm9\text{ cm}, and 12 cm12\text{ cm}.

  • What are the different ways they can be joined to get a quadrilateral?
  • Are you able to identify the different quadrilaterals that are obtained by joining the triangles? Justify your answer whenever you identify a quadrilateral.
Q8

Which Quad?

Gameplay

  1. Fold a sheet into half.
  2. Now, fold it once more into a quarter.
  3. Make a triangular crease at the corner that is at the middle of the paper.
  4. Open the sheet. What is the shape formed by the creases?
  5. How would you fold the quarter paper to get the kinds of creases shown in the following image.
  6. How would you fold the quarter paper such that a square is formed?
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