Q. If normal to the curve $y = f(x)$ is parallel to $x$-axis, then
A) $\frac{dy}{dx} = 0$
B) $\frac{dy}{dx} = 1$
C) $\frac{dx}{dy} = 0$
D) None of these
Explanation
(c)
Slope of the normal$= - \frac{1}{\left( \frac{dy}{dx} \right)}$
This is parallel to $x$-axis
$\Rightarrow \ \ - \frac{1}{\left( \frac{dy}{dx} \right)} = 0\ \ \ \Rightarrow \ \frac{dx}{dy} = 0$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.