Worked Example 1
Plot A(2, 1), B(6, 1), C(6, 4) and D(2, 4). What shape is ABCD, and what is its area?
Step 1: plot each point from the originPlot each one from the origin, never counting on from the previous point.
Step 2: look at what the coordinates tell youShared y-coordinates mean horizontal lines; shared x-coordinates mean vertical lines. So all four angles are right angles.
Step 3: name the shapeAB = 4 units, AD = 3 units, four right angles: a rectangle.
Step 4: areaArea = 4 x 3 = 12 square units, found by subtracting coordinates rather than measuring.
Worked Example 2
P(1, 3), Q(1, 8) and R(5, 3) are three corners of a rectangle. Find the fourth.
See how the given points relatePQ is vertical, PR is horizontal, and P is the corner where they meet.
Work out the missing cornerS takes its x from R and its y from Q, so S = (5, 8).
Check by plottingSides of 4 and 5, so area 20 square units and perimeter 18 units.