103 TRIGONOMETRY PROBLEMS

103 TRIGONOMETRY PROBLEMS

From the Training of the USA IMO Team
Titu Andreescu
Zuming Feng

CONTENTS

1 Trigonometric Fundamentals 1
Definitions of Trigonometric Functions in Terms of Right Triangles 1
Think Within the Box 4
You’ve Got the Right Angle 6
Think Along the Unit Circle 10
Graphs of Trigonometric Functions 14
The Extended Law of Sines 18
Area and Ptolemy’s Theorem 19
Existence, Uniqueness, and Trigonometric Substitutions 23
Ceva’s Theorem 28
Think Outside the Box 33
Menelaus’s Theorem 33
The Law of Cosines 34
Stewart’s Theorem 35
Heron’s Formula and Brahmagupta’s Formula 37
Brocard Points 39
Vectors 41
The Dot Product and the Vector Form of the Law of Cosines 46
The Cauchy–Schwarz Inequality 47
Radians and an Important Limit 47
Constructing Sinusoidal Curves with a Straightedge 50
Three Dimensional Coordinate Systems 51
Traveling on Earth 55
Where Are You? 57
De Moivre’s Formula 58
2 Introductory Problems 63
3 Advanced Problems 73
4 Solutions to Introductory Problems 83
5 Solutions to Advanced Problems 125

Glossary 199
Further Reading 211