Head First 2D Geometry

the index

perpendicular lines, 6, 106

(see also right angles)

Pi symbol (π), 214–216

pizza example, 206–233

comparing pizza sizes and prices, 223–232

comparing slice sizes and prices, 207–211

pepperoni crust prices, 212–221

polygons, 275

(see also regular polygons)

problems, methods of solving, 108–112, 116–118

proportional shapes, 73–76

Pythagoras/Pythagorus (see Pythagorean Theorem)

Pythagorean Theorem, 131–135, 138, 141–146,

148, 194

Pythagorean triples (Super Triangles), 146, 148

Q

quadrilaterals, 268, 272

corner angles of, adding, 34–37, 46

types of, 268–270

(see also squares)

R

radius of circle, 208, 234

range of speakers, 170–172

ratios, 73, 92–98

rectangles, 156–162, 269, 272

regular polygons, 275–276

apothem of, 306, 308, 312, 318

area of, 280–282, 284, 302–310, 312, 318

circles as, 298, 312

circumradius of, 306, 308, 312, 318

comparing to circles, 303–306

congruent triangles in, 302

internal angles in, 313–314, 318

perimeter of, 277, 284, 310–312, 318

side lengths of, 315–316

(see also equilateral triangles; squares)

rhombuses, 268, 270, 272

right triangles, 110–115, 119–131

integer vs. non-integer solutions for, 136

Pythagorean Theorem and, 131–135, 138, 141–146, 148

right angles, 6, 106

markings for, 6, 46

pairs of, 11, 14

(see also perpendicular lines)

rock festival example, 150–201

area of field shapes, 156–168

fence prices for field shapes, 151–154

location for drinks stall, 181–189

screen for obstructed view area, 190–200

speaker range and spread, 170–180

rope swing example, 139–147

S

scalene triangles, 194–198

scaling shapes, 70–76, 121–122

(see also similar shapes)

sectors of circle, 210, 226–228, 232, 234

septagons, 298

(see also regular polygons)

7-sided shapes (see septagons)

shapes

area of (see area)

congruent (see congruent shapes)

324 Index