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Evaluate : sin^(2)25^(@)+sin^(2)65^(@)+...

Evaluate : `sin^(2)25^(@)+sin^(2)65^(@)+sqrt(3)tan5^(@)tan15^(@)tan30^(@)tan75^(@)tan85^(@)`

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To evaluate the expression \( \sin^2(25^\circ) + \sin^2(65^\circ) + \sqrt{3} \tan(5^\circ) \tan(15^\circ) \tan(30^\circ) \tan(75^\circ) \tan(85^\circ) \), we can follow these steps: ### Step 1: Simplify \( \sin^2(25^\circ) + \sin^2(65^\circ) \) Using the identity \( \sin(90^\circ - x) = \cos(x) \), we have: \[ \sin(65^\circ) = \cos(25^\circ) \] Thus, \[ \sin^2(65^\circ) = \cos^2(25^\circ) \] Now, we can rewrite the expression: \[ \sin^2(25^\circ) + \sin^2(65^\circ) = \sin^2(25^\circ) + \cos^2(25^\circ) \] Using the Pythagorean identity \( \sin^2(x) + \cos^2(x) = 1 \): \[ \sin^2(25^\circ) + \cos^2(25^\circ) = 1 \] ### Step 2: Simplify \( \sqrt{3} \tan(5^\circ) \tan(15^\circ) \tan(30^\circ) \tan(75^\circ) \tan(85^\circ) \) Using the identity \( \tan(90^\circ - x) = \cot(x) \), we have: \[ \tan(75^\circ) = \cot(15^\circ) \quad \text{and} \quad \tan(85^\circ) = \cot(5^\circ) \] Thus, \[ \tan(75^\circ) \tan(15^\circ) = 1 \quad \text{and} \quad \tan(85^\circ) \tan(5^\circ) = 1 \] So we can rewrite: \[ \tan(5^\circ) \tan(15^\circ) \tan(30^\circ) \tan(75^\circ) \tan(85^\circ) = \tan(5^\circ) \cdot \tan(15^\circ) \cdot \tan(30^\circ) \cdot \cot(15^\circ) \cdot \cot(5^\circ) \] This simplifies to: \[ \tan(30^\circ) \] Now, we know that \( \tan(30^\circ) = \frac{1}{\sqrt{3}} \), so: \[ \sqrt{3} \tan(5^\circ) \tan(15^\circ) \tan(30^\circ) \tan(75^\circ) \tan(85^\circ) = \sqrt{3} \cdot \frac{1}{\sqrt{3}} = 1 \] ### Step 3: Combine the results Now we can combine the results from Step 1 and Step 2: \[ \sin^2(25^\circ) + \sin^2(65^\circ) + \sqrt{3} \tan(5^\circ) \tan(15^\circ) \tan(30^\circ) \tan(75^\circ) \tan(85^\circ) = 1 + 1 = 2 \] ### Final Answer Thus, the final answer is: \[ \boxed{2} \]
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