Playing with Constructions | A

Question 9

In your experimentation, did you consider the case when all four sides of the rectangle are equal? That is, did you consider the case of a square? See what happens in this special case!

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Solution

A square is a special rectangle. All its four sides are equal.

Step 1 — Understanding a Square

Let us think about a rectangle. It has a length and a width. We can call the length LL. We can call the width WW. For a square, all four sides are equal. So, its length and width must be the same. Let us call this side length ss. So, L=sL = s. And W=sW = s.

Diagram 1

Step 2 — Perimeter of a Square

The perimeter of a rectangle is 2×(length+width)2 \times (\text{length} + \text{width}). For a square, length is ss. Width is also ss. So, we put ss for length and ss for width.

Perimeter=2×(s+s)\text{Perimeter} = 2 \times (s + s)

=2×(2s)= 2 \times (2s)

Perimeter=4s\boxed{\text{Perimeter} = 4s}

Step 3 — Area of a Square

The area of a rectangle is length×width\text{length} \times \text{width}. For a square, length is ss. Width is also ss. So, we multiply ss by ss.

Area=s×s\text{Area} = s \times s

Area=s2\boxed{\text{Area} = s^2}

Answer

When a rectangle becomes a square: Its length and width become equal. We can call this common side length ss. The perimeter becomes 4s4s. The area becomes s×ss \times s, or s2s^2.

More questions in A

Q1

Observe the following figures and try drawing them freehand.

Q2

Mark a point ‘P’ in your notebook. Then, mark as many points as possible, in different directions, that are 4 cm away from P.

Think: Imagine marking all the points of 4 cm distance from the point P. How would they look?

Try to draw it and verify if it is correct by taking some points on the curve and checking if their distances from P are indeed 4 cm. Explore, if you have not already done so, and see if a compass can be used for this purpose.

You can start by marking a few points of distance 4 cm from P using the compass. How can this be done?

Q3

Having explored the use of a compass, go ahead and recreate the images in Fig. 8.1. Can you make the figures look as good as the figures shown there? Try again if you want to!

Also, has the use of instruments made the construction easier?

Q4

Construct

1. A Person

How will you draw this?

Q5

2. Wavy Wave

Construct this.

Q6

Make other artwork of your choice with a ruler and a compass.

Q7

Explore

How should the rectangle be constructed so that the diagonal divides the opposite angles into equal parts?

Q8

How will you record your observations? First, identify the parameters that need to be tracked. They are the sides of the rectangle and the 8 angles formed by the two diagonals. Are there any other measurements that you would want to keep track of?

Q9

In your experimentation, did you consider the case when all four sides of the rectangle are equal? That is, did you consider the case of a square? See what happens in this special case!

Q10

Math Talk

What general laws did you observe with respect to the angles and sides? Try to frame and discuss them with your classmates.

How can one be sure if the laws that you have observed will always be true?

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