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KCET · Maths · Application of Derivatives

The equation of the curve passing through the point \( (1,1) \) such that the slope of the tangent at
any point \( (x, y) \) is equal to the product of its co-ordinates is

  1. A \( 2 \log y=x^{2}+1 \)
  2. B \( 2 \log x=y^{2}+1 \)
  3. C \( 2 \log x=y^{2}-1 \)
  4. D \( 2 \log y=x^{2}-1 \)
Verified Solution

Answer & Solution

Correct Answer

(D) \( 2 \log y=x^{2}-1 \)

Step-by-step Solution

Detailed explanation

\(\frac{d y}{d x}=x y\)
\(\frac{1}{y} d y=x d x\)
Integrate
\(\log y=\frac{x^{2}}{2}+C \ldots(1)\)
Equation \((1)\) passing through \((1,1)\)
\(\log (1)=\frac{1^{2}}{2}+C\)
\(0=\frac{1}{2}+C\)
\(C=-\frac{1}{2}\)
\(\log y=\frac{\chi^{2}}{2}-\frac{1}{2}\)
\(2 \log y=\chi^{2}-1\)