Head First 2D Geometry

this is the index 321

Index

Symbols

∞ (infinity symbol), 298

π (Pi symbol), 214–216

Numbers

3D shapes, volume of, 278–280

3-sided shapes (see triangles)

4-sided shapes (see quadrilaterals; squares)

6-sided shapes (see hexagons)

7-sided shapes (see septagons)

8-sided shapes (see octagons)

9-sided shapes (see nonagons)

A

accurate construction, 108–112

acute angles, 10

acute triangles, 131, 148

adjacent angles, 9

altitude line, 144–145, 148

angles, 3

acute angles, 10

adding, 7–10

adjacent angles, 9

complementary angles, 9–10, 12–13, 47

cutting into smaller angles, 7, 46

equal angles, 30

of equilateral triangles, 176

of parallelograms, 246, 251

of quadrilaterals, adding, 34–37, 46

in regular polygons, 313–314, 318

right angles, 6, 11, 14, 46, 106

spread angle of speakers, 170–172, 174

of straight lines, 11, 46

supplementary angles, 17–18, 47

of triangles, adding, 20–22, 46

of triangles, estimating, 175–180

vertical angles, 19, 22, 47

apothem of regular polygon, 306, 308, 312, 318

arc of circle, 219–222, 234

area

of circles, 223–232, 234, 288, 310

compared to perimeter, 250, 309–310

of congruent triangles, 159

of equilateral triangles, 290–294, 318

of kites, 253–259

of parallelograms, 238–246

of rectangles, 156–162

of regular polygons, 280–282, 284, 302–310, 312, 318

of scalene triangles, 196

of sectors of a circle, 232, 234

of squares, 286

of trapezoids, 260–265

of triangles, 162–167, 202, 290–294

B

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