Trigonometrical Equations
medium

ગણ $S=\left\{x \in R : 2 \cos \left(\frac{x^{2}+x}{6}\right)=4^{x}+4^{-x}\right\}$ ની સભ્ય સંખ્યા $.....$ થાય.

A

$1$

B

$3$

C

$0$

D

અનંત

(JEE MAIN-2022)

Solution

$2 \cos \left(\frac{x^{2}+x}{6}\right)=4^{x}+4^{-x}$

L.H.S $\leq 2 . \&$ R.H.S. $\geq 2$

Hence L.H.S $=2$ \& R.H.S $=2$

$2 \cos \left(\frac{x^{2}+x}{6}\right)=2 \quad 4^{x}+4^{-x}=2$

Check $x=0$ Possible hence only one solution.

Standard 11
Mathematics

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