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MHT CET · Maths · Straight Lines

The abscissa of the point on the curve \(y=\mathrm{a}\left(\mathrm{e}^{\frac{x}{a}}+\mathrm{e}^{-\frac{x}{a}}\right)\) where the tangent is parallel to the X -axis is

  1. A 0
  2. B a
  3. C 2 a
  4. D -2 a
Verified Solution

Answer & Solution

Correct Answer

(A) 0

Step-by-step Solution

Detailed explanation

\(\begin{aligned}
& \quad y=\mathrm{a}\left(\mathrm{e}^{\frac{x}{a}}+\mathrm{e}^{\frac{-x}{a}}\right) \\
& \therefore \quad \frac{\mathrm{d} y}{\mathrm{~d} x}=\mathrm{e}^{\frac{x}{a}}-\mathrm{e}^{-\frac{x}{a}}
\end{aligned}\)
Since the tangent is parallel to X -axis, \(\frac{\mathrm{d} y}{\mathrm{~d} x}=0\)
\(\begin{aligned}
& \Rightarrow \mathrm{e}^{\frac{x}{\mathrm{a}}}-\mathrm{e}^{-\frac{x}{\mathrm{a}}}=0 \\
& \Rightarrow \mathrm{e}^{\frac{2 x}{\mathrm{a}}}=0 \\
& \Rightarrow x=0
\end{aligned}\)