Classify an angle by its measure Given the measure of an angle, name it: acute, right, obtuse or straight.
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Measure an angle with a protractor Read the measure of the angle shown on the protractor. Values are in steps of 10° (from 20° to 160°).
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Angle sum in a quadrilateral You know three angles of a quadrilateral. Work out the fourth — the sum is always 360°.
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Angle sum in a triangle You know two angles of a triangle. Work out the third — the sum is always 180°.
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Vertical and supplementary angles Two crossing lines form pairs of angles. Vertical (opposite) angles are equal; supplementary (adjacent on the same line) angles add to 180°.
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