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Trigonometrical Equations
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સમીકરણ $(s)$ of the equation ${\cos ^2}2x + {\cos ^2}\frac{{5x}}{4} = \cos 2x\,{\cos ^2}5x$ ના $\left[ {0,\frac{\pi }{3}} \right]$ માં કેટલા ઉકેલો મળે?
A
$0$
B
$1$
C
$2$
D
$3$
Solution
$\left( {{{\cos }^2}2x – \cos x{{\cos }^2}5x + {{\cos }^4}\frac{{5x}}{4}} \right) + \frac{{{{\cos }^2}5x\left( {1 – {{\cos }^2}5x} \right)}}{4} = 0$
$\cos 2 x=\frac{\cos ^{2} 5 x}{2} \& \sin 10 x=0$
$x=\frac{n \pi}{10}$
$x=0, \frac{\pi}{10}, \frac{2 \pi}{10^{\prime}} \frac{3 \pi}{10}$
No solution
Standard 11
Mathematics