WE KNOW PRODUCT OF SLOPE OF TWO PERPENDICULAR LINES IS -1.BUT LINES PARLLEL TO Y-AXIS AND X-AXIS R ALSO PERPENDICULAR WHY THEY DO NOT HAVE PRODUCT OF SLOPE = -1
WE KNOW PRODUCT OF SLOPE OF TWO PERPENDICULAR LINES IS -1.BUT LINES PARLLEL TO Y-AXIS AND X-AXIS R ALSO PERPENDICULAR WHY THEY DO NOT HAVE PRODUCT OF SLOPE = -1