Number of integral values of for which f (x)=ln(2 cos ,x+5) is de… - Vidyadip

MCQ

Number of integral values of $\lambda$ for which $f (x)=\sqrt {ln(2\lambda cos\,x+5)}$ is defined for all $x \in R$ is

✓
$5$
B
$4$
C
$6$
D
$11$

✓

Answer

Correct option: A.

$5$

a
$f(x) = \sqrt {\ell n(2\lambda \cos x + 5)} $

Nece. condition $2 \lambda \cos x+5 \geq 1$

$\Rightarrow \lambda \cos x>-2 \forall x \in R . $

$\lambda=0, \pm 1, \pm 2$

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