TABLE OF CONTENTS Up to this point we have been learning the language of mathematics and laying the foundation for trigonometry. Along the way we have discussed arithmetic, relationships and operations of numbers; algebra, a type of generalized arithmetic involving both constant numbers and variables; and geometry, the study of forms and relationships of plane figures.
Trigonometry is a branch of mathematics that includes arithmetic, algebra, and geometry, but is primarily concerned with the relationships of lines and angles in triangles. It is the basis of measurements used in surveying, engineering, shop mechanics, geodesy, and astronomy. The word trigonometry comes from the Greek words trigonon, a triangle, and metron, to measure.
trigon ? ?
metron ? measure
We begin our exploration of trigonometry by focusing strictly on right triangles, which form the basis for all trigonometric calculations. Recall that a right triangle is any triangle with a 90 angle. The standard right triangle is illustrated in Figure 20.1. Note that the three angles are labeled by the capital letters A, B, and C. Sometimes the three-letter convention is used to name the angles, in which case the vertex is the center letter, as in ? ABC also referred to as ? B. When the three vertices are used to name a right triangle, the vertex containing the right angle is sometimes underlined as in triangle A C B. By convention, ? C
