ABSTRACT
By drawing up tables of values from 0◦ to 360◦, graphs of y = sin A, y = cos A and y = tan A may be plotted. Values obtained with a calculator (correct to 3 decimal places – which is more than sufficient for plotting graphs), using 30◦ intervals, are shown below, with the respective graphs shown in Figure 39.1
From Figure 39.1 it is seen that
(a) Sine and cosine graphs oscillate between peak values of ±1
(b) The curve
(c) The sine and cosine curves are continuous and they repeat at intervals of 360◦ and the tangent curve appears to be discontinuous and repeats at intervals of 180◦
Figure 39.2 shows rectangular axes XX ′ and YY ′ intersecting at origin 0. As with graphical work, measurements made to the right and above 0 are positive, while those to the left and downwards are negative. Let 0A be free to rotate about 0. By convention, when 0A moves anticlockwise angular measurement is considered positive, and vice versa.
