Problem:Surveying Mathematics: Trigonometry

Problem: Surveying Mathematics: Trigonometry

In an equilateral triangle, what is the since of half of any one of the interior angles?

(A) 0.866
(B) 1.000
(C) 0.707
(D) 0.500

This is problem 12(1-8) from the new second edition of1001 Solved Surveying Problemsby Jan Van Sickle. Reprinted with permission from1001 Solved Surveying Problemsby Jan Van Sickle (1997, 728 pp., Professional Publications Inc.). For details on this and other FLS exam-prep books, call 800/426-1178 or

Answer: D

In an equilateral triangle, all sides and all angles are equal. Since the sum of the angles must be 180º, each angle of an equilateral triangle must be one-third of 180º, or 60º. The sine of 30º is 0.500.