ExamBro
ExamBro
TS EAMCET · Maths · Application of Derivatives

\(y=f(x)\) and \(x=g(y)\) are two curves and \(P(x, y)\) is a common point of the two curves. If at \(P\), on the curve \(y=f(x), \frac{d y}{d x}=Q(x)\) and at the same point \(P\) on the curve \(x=g(y), \frac{d x}{d y}=-Q(x)\), then

  1. A the two curves have a common tangent
  2. B the angle between two curves is \(45^{\circ}\)
  3. C tangent drawn at \(P\) to one curve is normal to the other curve at \(P\)
  4. D the two curves never intersect orthogonally
Verified Solution

Answer & Solution

Correct Answer

(C) tangent drawn at \(P\) to one curve is normal to the other curve at \(P\)

Step-by-step Solution

Detailed explanation

At point \(P\) : \(\begin{aligned} & y=f(x), \frac{d y}{d x}=\mathrm{Q}(x) \\ & x=g(y), \frac{d x}{d y}=-\mathrm{Q}(x) \Rightarrow \frac{d y}{d x}=\frac{1}{-\mathrm{Q}(x)}\end{aligned}\) \(\therefore\) Tangent drawn at \(P\) to one curve is normal to the other curve