Playing with Constructions | A

Question 5

2. Wavy Wave

Construct this.

Question diagram 1
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Solution
Understand the Question

The task is to construct a wavy wave pattern using geometric tools. The design consists of a horizontal baseline with two connected, alternating semicircles (one curving above the baseline and one curving below) filled with vertical line shading.

Step 1 · Draw the Baseline and Mark Points

Draw a straight horizontal baseline.Diagram 1

  1. Mark a starting point AA on the line.
  2. Measure 4 units4\text{ units} to the right of AA and mark point BB.
  3. Measure another 4 units4\text{ units} to the right of BB and mark point DD.

Step 2 · Draw the First Semicircle Above the Line

Find the center and construct the upper semicircle.Diagram 2

  1. Find the midpoint of segment ABAB: Radius=4 units2=2 units\text{Radius} = \dfrac{4\text{ units}}{2} = 2\text{ units}
  2. Mark this midpoint as C1C_1.
  3. Place the compass needle at C1C_1, set the radius to 2 units2\text{ units} (reaching point AA), and draw a semicircle above the line from AA to BB.

Step 3 · Draw the Second Semicircle Below the Line

Find the center and construct the lower semicircle.Diagram 3

  1. Find the midpoint of segment BDBD: Radius=4 units2=2 units\text{Radius} = \dfrac{4\text{ units}}{2} = 2\text{ units}
  2. Mark this midpoint as C2C_2.
  3. Place the compass needle at C2C_2, set the radius to 2 units2\text{ units} (reaching point BB), and draw a semicircle below the line from BB to DD.

Step 4 · Draw Vertical Shading Lines

Fill both semicircles with evenly spaced vertical lines.Diagram 4

  1. Mark equally spaced points along segment ABAB and draw vertical lines upwards until they touch the upper semicircle.
  2. Mark equally spaced points along segment BDBD and draw vertical lines downwards until they touch the lower semicircle.
Answer

The wavy wave pattern is constructed using two alternating semicircles of radius 2 units2\text{ units} filled with vertical lines.

Common Mistakes
  • Drawing on the Same Side: Drawing both semicircles on top of the baseline instead of alternating one above (ABAB) and one below (BDBD) to create the wave.
  • Radius Error: Using the full segment length (4 units4\text{ units}) as the compass radius instead of halving it to find the radius (2 units2\text{ units}).

More questions in A

Q1

Observe the following figures and try drawing them freehand.

Q2

Mark a point PP in your notebook. Then, mark as many points as possible, in different directions, that are 4 cm4\text{ cm} away from PP.

Think: Imagine marking all the points of 4 cm4\text{ cm} distance from the point PP. 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 PP are indeed 4 cm4\text{ 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 cm4\text{ cm} from PP 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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