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Head First 2D Geometry by Dawn Griffiths, Stray

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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

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