106
Plotting points on the coordinate grid
Textbook: Part 3, lesson 106, pp. 115–116
GoalPlotting points on the coordinate grid and joining them to make a shape.
New words
plot a point · nuqta yasashto join · tutashtirmoqcode · shifrvertex · uch
Explanation
To plot a point we go right along OX by the first coordinate, then up by the second coordinate, and mark the point. If we join points in the given order with a broken line, a shape appears. A shape can be “coded” by a list of points: we write only the coordinates of its vertices. Points with the same second coordinate lie on a horizontal line, points with the same first coordinate lie on a vertical line.
Worked examples
(2; 1) → (2; 4) → (5; 4) → (5; 1) → (2; 1): the shape is a square with side 3 units. Its perimeter is 4 × 3 = 12.
(4; 1), (4; 3), (4; 6) have the same first coordinate – they lie on a vertical straight line.
Class activity
“Picture code”: children draw a simple shape (house, star, flower) on squared paper and write the coordinates of the vertices. They give the code to a partner, who plots it and finds the picture.
Practice
1
The points (1; 1), (1; 4), (4; 4), (4; 1) are joined in turn to make a square. What is its perimeter in units?
12
2
How many units long is the segment joining (1; 1) and (5; 1)?
4
3
A rectangle has vertices A(1; 2), B(1; 5), C(6; 5). Write the coordinates of the fourth vertex D.
(6; 2)
4
On what kind of line do the points (4; 1), (4; 3), (4; 6) lie?
On a vertical straight line
5
A secretary types 180 words in 3 minutes. In how many minutes does she type 900 words?
15