Essentials of trigonometry / Irving Drooyan, Walter Hadel, Charles C. Carico. Drooyan, Irving. Hadel, Walter, joint author. Carico, Charles C., joint author. Plane trigonometry. QA533 .D74 1977 516.24 D786e "A portion of this material has been adapted from Trigonometry: an analytical approach." Includes index. New York : Macmillan, c1977. c1977. 1977 Text viii, 328 p. : eng