Machinery's Handbook, 31st Edition
TRIGONOMETRY
95
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Note: Base angles are designated as θ in the table below. The values are approximated to three decimal places. If more accuracy is needed, then calculator values carried out further can be used.
Functions of Angles Right Triangle Ratios.— Trigonometry is the branch of mathematics that addresses the relations of the sides and angles of triangles and the resulting functions of angles. The properties of trigonometry are derived, however, from the relationships of angles and
sides in the right triangle, as pictured here. In a right triangle, the 90 ° angle, C , is oppo- site the longest side, c , the hypotenuse . Since the sum of angle measures in any triangle is 180°, the sum of the two acute angles is 90°. The shorter sides, a and b, are called the legs . They are opposite to angles A and B , respec- tively. By the Pythagorean theorem, the sum of the squares of the legs is equal to the square of the hypotenuse; that is,
B
a
C = 90˚
A
b
a 2 + b 2 = c 2
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