Drooyan, Irving. <br/><br/>
Essentials of trigonometry / 
Irving Drooyan, Walter Hadel, Charles C. Carico. 
 - 2d ed. 
 - New York :  Macmillan,  c1977. 
 - viii, 328 p. :  ill. 
<br/><br/> "A portion of this material has been adapted from Trigonometry: an analytical approach." 
<br/><br/><label>ISBN: </label>0023302208 
<br/><br/><label>LCCN: </label>75030627 //r93 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Plane trigonometry.