Mathematics for IGCSE & O level - Geometrical Constructions (Section 2 - No. 5)
When using a protractor, how do you ensure an accurate measurement?
Estimate the angle size first, and align the zero line with one arm of the angle.
Use the outer scale only.
Measure the angle from the vertex.
Use the wrong scale on the protractor.
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Proper alignment and estimation are key to precise measurement.