The acute angle between intersecting lines that do not cross at right angles is the same as the angle determined by vectors norm
al to the lines or by the vectors parallel to the lines. Also, note that the vector ai + bj is perpendicular to the line ax + by = c Find the acute angles between the lines: x + √3y = 1 and (1 - √3)x + (1 + √3)y = 8 Thank you!