Plot A(2, 3), B(−2, 3), C(−2, −1) and D(2, −1). Name the figure ABCD and find its perimeter.
How to lay out the answer. Follow the frame, then write it in your own words.
1 · Write what is given and what is to be found. Given: A(2, 3), B(−2, 3), C(−2, −1), D(2, −1). To find: the type of figure and its perimeter.
2 · Draw the figure. Draw the axes with a scale. Plot the four points and join A to B, B to C, C to D and D to A.
3 · Write the formula or theorem. On a horizontal line, distance = difference of the x-coordinates. On a vertical line, distance = difference of the y-coordinates.
4 · Find the sides.
AB = 2 − (−2) = 4 units (both have y = 3)
BC = 3 − (−1) = 4 units (both have x = −2)
CD = 4 units and DA = 4 units in the same way
5 · Name the figure. All four sides are 4 units. AB is horizontal and BC is vertical, so ∠B = 90°. Therefore ABCD is a square.
6 · Check and box the answer. ABCD is a square. Perimeter = 4 × 4 = 16 units.
Scoring tip: Write the scale on the graph and label every point. A neat, labelled graph earns marks before any working.
