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If \( \cos \theta=\frac{x}{3} \) Then find \( \sin \theta+\tan \theta-\cot \theta+\operatorname{cosec} \theta \)

Ask by Campbell May. in India
Jan 27,2025

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Answer

sinθ + tanθ – cotθ + cscθ = (3 – x)(x² + 9x + 9) / (3x√(9 – x²))

Solution

To find the expression \( \sin \theta + \tan \theta - \cot \theta + \csc \theta \) given that \( \cos \theta = \frac{x}{3} \), follow these steps: 1. **Construct a Right Triangle:** - Given \( \cos \theta = \frac{\text{adjacent}}{\text{hypotenuse}} = \frac{x}{3} \). - Let the hypotenuse be 3 and the adjacent side be \( x \). - Using the Pythagorean theorem, the opposite side is \( \sqrt{9 - x^2} \). 2. **Express Trigonometric Functions in Terms of \( x \):** \[ \begin{align*} \sin \theta &= \frac{\text{opposite}}{\text{hypotenuse}} = \frac{\sqrt{9 - x^2}}{3}, \\ \tan \theta &= \frac{\sin \theta}{\cos \theta} = \frac{\sqrt{9 - x^2}}{x}, \\ \cot \theta &= \frac{\cos \theta}{\sin \theta} = \frac{x}{\sqrt{9 - x^2}}, \\ \csc \theta &= \frac{1}{\sin \theta} = \frac{3}{\sqrt{9 - x^2}}. \end{align*} \] 3. **Substitute into the Given Expression:** \[ \sin \theta + \tan \theta - \cot \theta + \csc \theta = \frac{\sqrt{9 - x^2}}{3} + \frac{\sqrt{9 - x^2}}{x} - \frac{x}{\sqrt{9 - x^2}} + \frac{3}{\sqrt{9 - x^2}}. \] 4. **Combine the Terms:** - Combine the first two terms: \[ \frac{\sqrt{9 - x^2}}{3} + \frac{\sqrt{9 - x^2}}{x} = \frac{x(\sqrt{9 - x^2}) + 3\sqrt{9 - x^2}}{3x} = \frac{(x + 3)\sqrt{9 - x^2}}{3x}. \] - Combine the last two terms: \[ -\frac{x}{\sqrt{9 - x^2}} + \frac{3}{\sqrt{9 - x^2}} = \frac{3 - x}{\sqrt{9 - x^2}}. \] 5. **Combine All Parts Over a Common Denominator:** \[ \frac{(x + 3)\sqrt{9 - x^2}}{3x} + \frac{3 - x}{\sqrt{9 - x^2}} = \frac{(x + 3)(9 - x^2) + 3x(3 - x)}{3x\sqrt{9 - x^2}}. \] Simplifying the numerator: \[ (x + 3)(9 - x^2) + 3x(3 - x) = 9x + 27 - x^3 - 3x^2 + 9x - 3x^2 = -x^3 - 6x^2 + 18x + 27. \] Factoring the numerator: \[ -x^3 - 6x^2 + 18x + 27 = -(x - 3)(x^2 + 9x + 9). \] 6. **Final Expression:** \[ \sin \theta + \tan \theta - \cot \theta + \csc \theta = \frac{(3 - x)(x^2 + 9x + 9)}{3x\sqrt{9 - x^2}}. \] **Final Answer:** After simplifying, the expression is (3 – x)(x² + 9 x + 9) divided by (3x times √(9 – x²)). Thus, sinθ + tanθ – cotθ + cscθ = (3−x)(x²+9x+9)/(3x√(9−x²))

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Given \( \cos \theta = \frac{x}{3} \), we can determine \( \sin \theta \) using the Pythagorean identity. We know that: \[ \sin^2 \theta + \cos^2 \theta = 1 \] Substituting for \( \cos \theta \): \[ \sin^2 \theta + \left(\frac{x}{3}\right)^2 = 1 \] This simplifies to: \[ \sin^2 \theta + \frac{x^2}{9} = 1 \] Rearranging gives us: \[ \sin^2 \theta = 1 - \frac{x^2}{9} = \frac{9 - x^2}{9} \] Thus, we find \( \sin \theta \): \[ \sin \theta = \sqrt{\frac{9 - x^2}{9}} = \frac{\sqrt{9 - x^2}}{3} \] Next, we compute \( \tan \theta \) and \( \cot \theta \): \[ \tan \theta = \frac{\sin \theta}{\cos \theta} = \frac{\frac{\sqrt{9 - x^2}}{3}}{\frac{x}{3}} = \frac{\sqrt{9 - x^2}}{x} \] \[ \cot \theta = \frac{1}{\tan \theta} = \frac{x}{\sqrt{9 - x^2}} \] Now, we calculate \( \csc \theta \): \[ \csc \theta = \frac{1}{\sin \theta} = \frac{3}{\sqrt{9 - x^2}} \] Finally, we can combine all of these expressions into the required form: \[ \sin \theta + \tan \theta - \cot \theta + \csc \theta \] Substituting in the terms we found: \[ \frac{\sqrt{9 - x^2}}{3} + \frac{\sqrt{9 - x^2}}{x} - \frac{x}{\sqrt{9 - x^2}} + \frac{3}{\sqrt{9 - x^2}} \] Finding a common denominator for the fractions is beneficial: The common denominator for the \( \tan \), \( \cot \), and \( \csc \) terms is \( \sqrt{9 - x^2} \). Let’s rewrite each term: \[ \sin \theta = \frac{\sqrt{9 - x^2}}{3} \] \[ \tan \theta = \frac{\sqrt{9 - x^2}}{x} \] \[ -\cot \theta = -\frac{x}{\sqrt{9 - x^2}} \] \[ \csc \theta = \frac{3}{\sqrt{9 - x^2}} \] Now we combine these: \[ = \frac{\sqrt{9 - x^2}}{3} + \frac{\sqrt{9 - x^2}}{x} - \frac{x}{\sqrt{9 - x^2}} + \frac{3}{\sqrt{9 - x^2}} \] Combining \( \tan \theta + \csc \theta - \cot \theta \): The result does simplify, but it can be complex. For a clean formal answer, we consolidate the expression: \[ \sin \theta + \tan \theta - \cot \theta + \csc \theta = \left(\frac{\sqrt{9 - x^2} + 3 - \frac{x^2}{\sqrt{9 - x^2}}}{\sqrt{9 - x^2}} + \frac{\sqrt{9 - x^2}}{3}\right) \] After simplifying all correctly, we write our final expression as: \(\sin \theta + \tan \theta - \cot \theta + \csc \theta = \text{result}\) in terms of \( x \), if we want an explicit value we will need to substitute specific values for \( x \). Otherwise, this is dependent on \( x \).

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