0 If we let P continue to travel around U, the same pattern is repeated in the O-intervals [271, 471] and [471,671]' In general, the values of sin 0 repeat in all successive intervals of length 271.

Note that the line is vertical. A linear equation in x and y is an equation of the form ax + hy = c (or ax + hy + d = 0) , with a and h not both zero. The graph of a linear equation is a line . EXAMPLE 8 Find a linear equation for the line through A(I , 7) and B( - 3,2). 8)(ii). Using A(1 , 7) gives us y - 7 = -i-(x - 1), which is equivalent to 4y - 28 = 5x - 5, or 5x - 4y = - 23 . 1 ALGEBRA 1 1 EXAMPLE 9 (a) Find the slope of the line 1 with equation 2x - 5y = 9. (b) Find linear equations for thc lines through P(3 , - 4) that are parallel to 1 and perpendicular to I.