Section 1.2 Relations

Relation Relation is a set of points in the plane (graphical description) Roster method lists all of the points which belong to the relation R We write: R = { (-2,1),(4,3), (0,-3) } Roster description Graphical description

Example Graph the following relations HLS1 = { (x, 3) : -2 ≤ x ≤ 4} HLS2 = { (x, 3) : -2 ≤ x < 4} V = { (3, y): y is a real number}

Algebraic Description We can describe the points in V as those points which satisfy the equation x = 3 The equation y = -2 corresponds to all points in the plane whose y-coordinate is -2

Equations of Vertical and Horizontal Lines The graph of the equation x = a is a vertical line through (a,0) The graph of the equation y = b is a horizontal line through (0,b)

Example Graph the relation: R = { (x,y) : 1 < y ≤ 3 }