1. Directed magnitudes. The use of positive and negative numbers is a familiar method of indicating temperatures either above or below a certain fixed temperature, which is taken as the zero of the scale. In the same way, it is convenient to use positive and negative numbers to designate the measures of other magnitudes, the values of which may fall on either side of a certain fixed value, taken as a point of departure. For example, northern latitude may be designated as positive, southern latitude as negative; eastern longitude as positive, western longitude as negative; a credit balance as positive, a debit balance as negative; altitude above sea level as positive, altitude below sea level as negative, etc.2. Points on a line. Directed lines. A simple graphical representation of such magnitudes is obtained by means of a straight line, called the axis, upon which are indicated a fixed point, called the origin, a unit distance and a positive direction.O (Origin) 1 Table of Contents 1 Directed magnitudes 1; 2 Points on a line Directed Jines 1; 3, 4 Points in a plane 2; 5 A fundamental theorem 3; 6, 7 Projections of line segments 4; 8, 9 Directed angles _ 5; 10, 11 Radian measure 6; CHAPTER II; THE TRIGONOMETRIC RATIOS SIMPLE IDENTITIES; 12, 13 Standard position 9; 14-17 Trigonometric ratios 9; 18, 19 Reduction to the first quadrant 11; 20 Ratios of acute angles , 13; 21, 22 Ratios of 30°, 60°, and 45° 13; 23 Ratios of 90°, 180 °, 270 °, and 360° 15; 24, 25 Trigonometric functions 16; 26 Periodicity 17; 27, 28 Relations between the trigonometric functions 18; CHAPTER III LOGARITHMS; 29 Theory of exponents 20; 30 The use of exponents in calculation 21; 31, 32 Definition of logarithms 21; 33, 34 Fundamental theorems on logarithms 22; 35 Common logarithms 24; 36, 37 Use of a table of logarithms 26; 38, 39 Calculation by means of logarithms 28; 40, 41 The right triangle 32; 42 Accuracy of the c