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JEE Mains · Maths · STD 12 - 2. inverse trigonometric function

Let \(f(x)=2 \cos ^{-1} x+4 \cot ^{-1} x-3 x^{2}-2 x+10, x \in[-\) \(1,1]\). If \([ a , b ]\) is the range of the function then \(4 a -\) \(b\) is equal to

  1. A \(11\)
  2. B \(11-\pi\)
  3. C \(11+\pi\)
  4. D \(15-\pi\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(11-\pi\)

Step-by-step Solution

Detailed explanation

\(f^{\prime}(x)=\frac{-2}{\sqrt{1-x^{2}}}-\frac{4}{1+x^{2}}-6 x-2\) \(=-2\left[\frac{1}{\sqrt{1-x^{2}}}+\frac{2}{1+x^{2}}+3 x+1\right]\) \(f^{\prime}(x)<0 \Rightarrow f(x)\) is a dec. function \(f(1)=\pi+5\) \(f(-1)=5 \pi+5\) Range : \([ a , b ] \equiv[\pi+5,5 \pi+5]\)…
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