Question

If normal to the curve y = f(x) is parallel to x-axis, then correct statement is [RPET 2000]

• A. $\frac{dy}{dx}=0$
• B. $\frac{dy}{dx}=1$
• C. $\frac{dx}{dy}=0$
• D. None of these

Answer 1

The correct option is B $\frac{dy}{dx}=1$

$sinxsin3x=\frac{1}{2}[cos2x-cos4x].$