Straight Lines

The inclination is the angle made

The inclination is the angle made by a line with the positive direction of the x-axis, measured anticlockwise. Its value lies between 0 degrees and 18

If theta is the inclination

If theta is the inclination of a line, then slope m is tan theta. For two points (x1, y1) and (x2, y2) on a non-vertical line, m = (y2 - y1) / (x2 - x

Two non

Two non-vertical lines are parallel if and only if their slopes are equal. Two non-vertical lines are perpendicular if and only if the product of thei

If two non

If two non-vertical lines have slopes m1 and m2, the acute angle theta between them satisfies tan theta = |(m2 - m1) / (1 + m1m2)|, provided 1 + m1m2

A line can be written

A line can be written in several forms: point-slope form y - y0 = m(x - x0), two-point form y - y1 = [(y2 - y1)/(x2 - x1)](x - x1), slope-intercept fo