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Solve the Following Equation: Sin 2 X − Cos X = 1 4 - Mathematics

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प्रश्न

Solve the following equation:
\[\sin^2 x - \cos x = \frac{1}{4}\]

बेरीज
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उत्तर

\[\sin^2 x - \cos x = \frac{1}{4}\]
\[\Rightarrow 1 - \cos^2 x - \cos x = \frac{1}{4}\]
\[ \Rightarrow 4 - 4 \cos^2 x - 4 \cos x = 1\]
\[ \Rightarrow 4 \cos^2 x + 4 \cos x - 3 = 0\]
\[ \Rightarrow 4 \cos^2 x + 6 \cos x - 2 \cos x - 3 = 0\]
\[ \Rightarrow 2 \cos x(2 \cos x + 3) - 1(2 \cos x + 3) = 0\]
\[ \Rightarrow (2 \cos x + 3) (2 \cos x - 1) = 0\]
\[\Rightarrow (2 \cos x - 1) = 0\] or
\[2 \cos x + 3 = 0\]
\[\Rightarrow \cos x = \frac{1}{2}\] or
\[\cos x = - \frac{3}{2}\] is not possible.
\[\therefore \cos x = \frac{1}{2} \]
\[ \Rightarrow \cos x = \cos\frac{\pi}{3} \]
\[ \Rightarrow x = 2n\pi \pm \frac{\pi}{3}, n \in Z\]
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पाठ 11: Trigonometric equations - Exercise 11.1 [पृष्ठ २२]

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आरडी शर्मा Mathematics [English] Class 11
पाठ 11 Trigonometric equations
Exercise 11.1 | Q 3.1 | पृष्ठ २२

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