Q. For $x \in IR,3\cos{(4x - 5) + 4}$ lies in the interval
A) [1, 7]
B) [4, 7]
C) [0, 7]
D) [2, 7]
Explanation
(a)
Since, $- 1 \leq \cos{\theta \leq 1}$
$\therefore\ - 1 \leq \cos{(4x - 5) \leq 1}$
$\Rightarrow \ - 3 \leq 3\cos{(4x - 5) \leq 3}$
$\Rightarrow \ \ 4 - 3 \leq 3\cos{(4x - 5) + 4 \leq 3 + 4}$
$\Rightarrow \ \ 1 \leq 3\cos{(4x - 5) + 4 \leq 7}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.