29
The coordinate grid
Textbook: Part 1, lesson 29, pp. 90–92
GoalLocate points on a coordinate grid from their coordinates and build shapes.
New words
coordinate grid · koordinata burchagicoordinate · koordinatahorizontal ray · gorizontal nurvertical ray · vertikal nur
Explanation
Two perpendicular number rays form a coordinate grid. A point is given by two numbers: A(3; 5) means 3 units along the horizontal ray and 5 units along the vertical ray. The order matters: (3; 5) and (5; 3) are different points. Joining points with segments gives a shape whose perimeter and area we can find.
Worked examples
A(1; 1), B(5; 1), C(5; 4), D(1; 4) form a rectangle: AB = 4, BC = 3, P = (4 + 3) × 2 = 14, S = 4 × 3 = 12.
(3; 5) and (5; 3): the first is 3 right and 5 up; the second is 5 right and 3 up – different points.
Class activity
“Picture from points”: the teacher reads out a list of coordinates; children mark the points, join them in order and find what shape appears.
Practice
1
How many units apart are K(2; 3) and L(7; 3)?
5
2
A(1; 1), B(6; 1), C(6; 4), D(1; 4) form a rectangle. What is its perimeter in units?
16
3
What is the area of that rectangle in square units?
15
4
Which point do you reach from M(4; 6) by moving 2 units right and 1 unit down?
(6; 5)