Question

If normal to the curve y=f(x) is parallel to x-axis, then correct statement is

• A. $\frac{dy}{dx}=0$
• B. $\frac{dy}{dx}=1$
• C. $\frac{dx}{dy}=0$
• D. $Noneofthese$

Answer 1

The correct option is C $\frac{dx}{dy}=0$

Slope of the normal = $-\frac{1}{\left(\frac{dy}{dx}\right)}$
This is parallel to x-axis $\Rightarrow -\frac{1}{\left(\frac{dy}{dx}\right)}=0\Rightarrow \frac{dx}{dy}=0$