Maths · Geometry. The idea in plain words, the rules to remember, the mistake to avoid and a worked example, written and checked by Mega Lecture.
A construction is an accurate drawing made with a ruler and a pair of compasses. Compasses are used because every point on an arc is the same distance from the centre of the arc. To construct a triangle from three side lengths, draw one side, then draw an arc from each end. The point where the arcs cross is the third corner.
The arcs only cross if the two shorter sides together are longer than the longest side. The same idea explains a bisector: the arcs must be wide enough to meet.
A net is a flat shape that folds up to make a solid. The area of the net is the surface area of the solid.
Students rub out their construction arcs or use a protractor when the question says ruler and compasses only. Leave every arc on the page: the arcs are the working.
Answer: 132 cm2
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