Question

Number of integral values of $k$ for which the equation $4{\cos }^{-1}(-|x|)=k$ has exactly two solutions, is

• A. 4
• B. 5
• C. 6
• D. 7

Answer 1

Answer: (C)

Graph of $y=4{\cos }^{-1}(-|x|)$
From the graph it is
Clear that $k\in (2\pi ,4\pi ]$
$\therefore$ integral values of $k$ are $7,8,9,10,11,12$