TRIGONOMETRY

TRIGONOMETRY Our discussion will focus primarily on the study of plane trigonometry. It is intended only as a review of the relationships among the sides and angles of plane triangles and their ratios, called the TRIGONOMETRIC FUNCTIONS. The information presented here is based on Mathematics, Vol. 1, NAVEDTRA 10069-D1, chapter 19, and Mathematics, Vol. 2-A, NAVED- TRA 10062, chapters 3, 4, and 6. Spherical trigonometry will be covered as you advance in rate. It is a prerequisite to the study of navigation, geodesy, and astronomy. Hence, the subject of spherical trigonometry will be introduced in the Engineering Aid class C1 school curriculum. MEASURING ANGLES When two straight lines intersect, an angle is formed, You can also generate an angle by rotating a line having a set direction, Figure 1-19 depicts the generation of an angle. The terminal line OB is generated from the initial point OA and forms L AOB, which we will call 6 (Greek letter, pronounced “theta”). Angle 8 is generally ex- pressed in degrees. The following paragraphs will discuss the degree and the radian systems that are generally used by Engineering Aids. The DEGREE SYSTEM is the most common system used in angular measurement. Angular measurement by REVOLUTION is perhaps the unit you are most familiar with. In the degree system, a complete revolution is divided into 360 equal parts called degrees (360°). Each degree is divided into 60 minutes (60´), and each minute into 60 seconds (60”). For convenience in trigonometric computations, the 360° is divided into four parts of 90° each. The 1-16