# Straight lines - product of slope of perpendicular lines.

Let $l$ be a line with slope $\frac{1}{0}$, and $m$ a line with slope $0$. Now, line $l$ is perpendicular to line $l$, therefore the product of the slope of line $l$ and the slope of line $m$ equals $-1$. This implies that $\frac{1}{0} \times 0 = -1$! • the slope of the vertical line is not defined as division by zero is not defined Dec 19, 2016 at 6:58
• We can "prove" all sorts of things using division by zero... There is even a section on division by zero "proofs" at the Wikipedia Mathematical Fallacy page, which contains the famous "proof" that 1=2. Dec 19, 2016 at 7:18
• Why are you posting twice? 1/0 is not a number so you can't manipulate it arithmetically like that. If 1/0 x 0 equals anything, then it has to equal everything. But it doesn't equal anything. Dec 19, 2016 at 7:28
• Sorry my mistake. But that is not the answer to my question Dec 19, 2016 at 7:32
• Kanwaljit singh gave the answer with reasons..!! Dec 19, 2016 at 7:34