Term 1 review

Unit 3 facts. Triangles are congruent by SSS, SAS (the angle between the sides), ASA, AAS or RHS. Pythagoras: c² = a² + b²; the converse tests a triangle, and c² < a² + b² means acute, c² > a² + b² means obtuse. The midsegment joining two midpoints is parallel to the third side and half as long; the three medians meet at the centroid, which cuts each median 2 : 1 from the vertex; the median to the hypotenuse of a right-angled triangle is half the hypotenuse. In an isosceles triangle the base angles are equal; an equilateral triangle has three 60° angles; the 30°–60°–90° triangle has the short leg equal to half of the hypotenuse. A polygon has interior angle sum (n − 2) × 180°, exterior angle sum 360°, and a regular polygon has exterior angle 360° ÷ n. Unit 4 facts. Cumulative frequency is a running total plotted at the upper limits. Mean = total of f × m ÷ total of f; the median has rank total ÷ 2 and is found by proportion or from the curve; the mode comes from the crossing lines on the histogram.