Question

Product of slopes of two perpendicular lines is -1. Slope of x-axis is 0 and that of y-axis is ∞. So , how can be the product of 0 and ∞ equals -1?

Answer 1

See explanation.

Explanation:

The rule: "Product of slopes of perpendicular lines is `-1`" can only be used if both lines can be written as: `y=ax+b` (it means that both lines are graphs of a function). A graph `x=a` is not a function because it has more than one value (precisely infinitely many) for one argument `a`.