0.6 		Trigonometry (also see 5.3)

Factoring Functions, J. C. Bodenrader, 2:1, 1971, 23-26, 5.1.2, 3.2, 9.1
An Interesting Correspondence and Its Consequence, Sidney Penner, 2:1, 1971, 40-44
Pascal's Triangle, Karl J. Smith, 4:1, 1973, 1-13, 3.2, 9.2
A "Doodling" Inequality, Benjamin Greenberg, 4:1, 1973, 78-79, C
A Classroom Theorem on Trigonometric Irrationalities, Norman Schaumberger, 5:1, 1974, 73-76, C
Square Functions, Helmer Junghans, 5:2, 1974, 15-18, 0.7
A Set of Trigonometric Inequalities with Applications to Maxima and Minima, Norman Schaumberger, 5:3, 1974, 26-30, 5.1.4
A Generator of Trigonometric Identities, Aron Pinker, 5:4, 1974, 54-55, C
Mathematical Astronomy, Vincent J. Motto, 6:1, 1975, 21-26
Closing the Loopholes, Morton Bloomfield and Frank Lasak, 6:2, 1975, 42-44, C
An Interesting Use of Generating Functions, Aron Pinker, 6:4, 1975, 39-45, 5.4.2, 9.5
Closing the Loopholes in "Closing the Loopholes", Gene Zirkel, 7:3, 1976, 55-58, C
Another Note on "Closing the Loopholes", Larry F. Bennett, 7:3, 1976, 56-58, C
Quasi-Pythagorean Triples for an Oblique Triangle, Kay Dundas, 8:3, 1977, 152-155, 9.3
Geometric Proofs of the Formulas for Sin(x+y) and Cos(x+y), Norman Schaumberger, 10:1, 1979, 35, C
An Ellipse Problem Beyond the Reach of Calculus, Ivan Niven, 10:3, 1979, 162-168, 0.5
Why Can't We Trisect an Angle This Way?, David Beran, 10:3, 1979, 199-200, C
Products of Sines, Zalman Usiskin, 10:5, 1979, 334-340
Geometric Interpretations of Sin(phi1)+Sin(phi2)=1, Charles Muses, 10:5, 1979, 350-351, C
A Formula for Sin (A+B), Simon J. Lawrence, 11:2, 1980, 125-126, C
Formulas for sin(x+y) and cos(x+y), Robert Geist, 11:2, 1980, 126, C
Trigonometric Solutions to the Quadratic Equation, Leo Chosid, 11:5, 1980, 330-331, C
A Coordinate Geometry Evaluation of ABS(tan(A-B)), Norman Schaumberger, 12:1, 1981, 52-54, C
Applying Complex Arithmetic, Herbert L. Holden, 12:3, 1981, 190-194, 5.3.1, 9.3, 9.5
Visual Application of Sin(theta1 + theta2) = Sin(theta1)Cos(theta2) + Cos(theta1)Sin(theta2), Gerald E. Gannon, 12:3, 1981, 206, C
Sum Formulas for Sine and Cosine, Dan Kalman, 14:1, 1983, 55-56, C
The Steiner-Lehmus Theorem as a Challenge Problem, Ken Seydel and Carl Newman, 14:1, 1983, 72-75, 0.4
Approximation to an Angle Trisection, Glen Peterson, 14:2, 1983, 166-167, C
Integer-Sided Triangles with One Angle Twice Another, R. S. Luthar, 15:1, 1984, 5-56, C, 9.3
Proving Heron's Formula Tangentially, David E. Dobbs, 15:3, 1984, 252-253, C, 0.4
Approximate Angle Trisection, David Gauld, 15:5, 1984, 420-422, C, 5.4.2
Generalized Pythagorean Triples, W. J. Hildebrand, 16:1, 1985, 48-52, 5.5, 9.3
Pitfalls in Graphical Computation, or Why a Single Graph Isn't Enough, Franklin Demana and Bert K. Waits, 19:2, 1988, 177-183  
The Fundamental Periods of Sums of Periodic Functions, James Caveny and Warren Page, 20:1, 1989, 32-41, 9.5
The Double-Angles Formulas, Roger B. Nelsen, 20:1, 1989, 51, C
Lattices of Trigonometric Identities, William E. Rosenthal, 20:3, 1989, 232-234, C, 5.2.3
Where There is Pattern, There is Significance, Lloyd Olson, 20:4, 1989, 321, C
FFF #11. A New Trigonometric Identity, Ed Barbeau, 20:5, 1989, 404, F (also 22:2, 1991, 132-133,  30:3, 1999, 211)
(Sin x)^2: A Sheep in Wolf's Clothing, Mark E. Saul, 21:1, 1990, 43-44, C, 5.1.5
FFF #18. Glide-Reflection to Sine Curve, Ed Barbeau, 21:3, 1990, 216, F
China's 1989 National College Entrance Examination, Bart Braden, 21:5, 1990, 390-393, 0.2, 0.4, 1.2
Trigonometric Identities through Calculus, Herb Silverman, 21:5, 1990, 403, C, 5.3.1
A Productive Error in a Trigonometry Text, Lee H. Minor, 22:4, 1991, 315-318, C
FFF #54. A Degree of Differentiation, Ed Barbeau, 23:3, 1992, 203, F, 5.1.3 (also 23:4, 1992, 306 and 24:4, 1993, 345)
FFF.  A 21-41-50 Triangle, Ed Barbeau, 23:4, 1992, 304, F
Cos(s-t) from the Distance Formula, Gilbert Strang, 23:4, 1992, 333, C
The Half-Angle Formula for Cotangent, Fen Chen, 23:5, 1992, C
The Half-Angle Formulas for the Tangent, Sidney H. Kung, 25:3, 1994, 205, C
A Simple Geometric Proof of the Addition Formula for the Sine, Jeffrey Li-chieh Ho, 25:3, 1994, 229-230, C
An Early Iterative Method for the Determination of Sine of One Degree, Farhad Riahi, 26:1, 1995, 16-21, 2.1
cos(x+y) (Proof Without Words), Sidney H. Kung, 26:2, 1995, 145, C
The Double-Angle Formulas via the Laws of Sines and Cosines, Sidney H. Kung, 27:2, 1996, 155, C
A Complex Approach to the Laws of Sines and Cosines, William V. Grounds, 27:2, 1996, 108, C, 9.5
A Law of Cosines (Proof Without Words), S. H. Kung and Jingcheng Tong, 27:3, 1996, 219, C
FFF #122. On Not Identifying Equations and Identities, Richard Askey, 28:5, 1997, 377-379, F
Trigonometric Identity: The Difference of Two Sines or Two Cosines (proof without words), Yukio Kubayashi, 29:2, 1998, 133, C
Trigonometric Identity: The Sum of Two Sines or Two Cosines (proof without words), Yukio Kubayashi, 29:2, 1998, 157, C
Undersampled Sine Waves, J. C. Derderian and Enriqueta Rodriguez-Carrington, 29:3, 1998, 213-218, 5.1.5
FFF #130. Forces with a Given Resultant, Don Curran, 29:4, 1998, 301-302, F
FFF #133. Identifying the Angle, K. R. S. Sastry, 29:5, 1998, 405-406, F
Proof Without Words: tan(a-b), Guanshen Ren, 30:3, 1999, 212, C
A Simple Geometric Solution to De lÕHospitalÕs Pulley Problem, Raymond Boute, 30:4, 1999, 311-314, C, 0.3
Measuring the Curl of Paper, Joseph Paullet and Richard Bertram, 30:4, 1999, 315-317, C, 5.1.4
One Figure: Six Identities, Roger Nelsen, 31:2, 2000, 145-146, C
2 arctan(1/3)+arctan(1/7)=pi/4 (Mathematics Without Words), Norman Schaumberger, 31:5, 2000, 372, C
FFF #160. The perimeter of a triangle, Peiyi Zhao, 31:5, 2000, 393-394, F
FFF #161. Conditions of equality, the editor, 31:5, 2000, 394, F
FFF #162. Proof that a 3-4-5 right triangle does not exist, Jeff Suzuki, 31:5, 2000, 394-395, F
Solution of a Triangle (Mathematics Without Words), Rex Wu, 32:1, 2001, 68-69, C
sin A + sin B + sin C (Mathematics Without Words), Norman Schaumberger, 32:3, 2001, 222, C
Law of Tangents (Mathematics Without Words), Roger Nelsen, 32:3, 2001, 237, C
FFF #176. A Trigonometric Reduction, J. Sriskandarajah, 32:4, 2001, 282, F
HeronÕs Formula via Proofs Without Words, Roger B. Nelsen, 32:4, 2001, 290-292, C, 0.3
The Volume of a Tetrahedron, Cho Jinsok, 32:4, 2001, 294-296, C, 0.4
Geometric Progressions Š A Geometric Approach, Michael Strizhevsky and Dmitry Kreslavskiy, 32:5, 2001, 359-362, 5.4.2
Was Calculus Invented in India?, David Bressoud, 33:1, 2002, 2-13, 2.2, 5.4.3
A Sum of Inverse Tangents (Mathematics Without Words), Geoffrey A. Kandall, 33:1, 2002, 13, C
Solutions to x+y=xy (Mathematics Without Words), Roger Nelsen, 33:2, 2002, 130, C, 0.2
FFF #196. A new proof of an old identity, Anand Kumar, 33:4, 2002, 309, F
Exact Value for the Sine and Cosine of Multiples of 18 degrees Š A Geometric Approach, Brian Bradie, 33:4, 2002, 318-319, C
An Identity of Euler, Don Goldberg, 33:4, 2002, 345, C
The Sine of a Sum from the Law of Sines, James Kirby, 33:5, 2002, 383, C
Arctan(n/m) (Mathematics Without Words), Roger Nelsen, 34:1, 2003, 10, C
A Tangent Identity (Mathematics Without Words), Roger Nelsen, 34:3, 2003, 193, C
A Triple Angle Formula for Tangent, Yuichiro Kakihara, 34:3, 2003, 227-228, C
Predicting Sunrise and Sunset Times, Donald A. Teets, 34:4, 2003, 317-321, C, 0.4
Proof Without Words: Sine and Cosine Sums That Equal 0, Tingyao Zheng, 35:2, 2004, 96, C
Some trigonometric facts (Proof Without Words), Larry Hoehn, 35:4, 2004, 282, C
On a Common Mnemonic from Trigonometry, Eugene C. Boman and Richard Brazier, 35:4, 2004, 302-303, C
The Theorem of Cosines for Pyramids, Alexander Kheyfits, 35:5, 2004, 385-388, C, 0.4
Trigonometric Identities on a Graphing Calculator, Joan Weiss, 35:5, 2004, 393-396, C, 5.1.5
FFF #238. Important knowledge about triangles, Associated Press, 36:2, 2005, 143, F
FFF #259. The additive formula for sine, Juan Tolosa, 37:5, 2006, 383, F
A Geometric View of Complex Trigonometric Functions, Richard Hammack, 38:3, 2007, 210-217, 4.3, 9.5
Two Problems with Table Saws, William R. Vautaw, 39:2, 2008, 121-128, 0.4, 5.1.3
The Right Theta, William Freed and Athanasios Tavouktsoglou, 39:2, 2008, 148-152, C (see also The Historical Theta Formula, R. B. Burckel and Zdislav Kovarik, 39:3, 2008, 229), 5.3.1, 5.7.3
An Elementary Trigonometric Equation, Victor H. Moll, 39:5, 2008, 395-399, C, 9.3