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Mathematics

Without using trigonometric tables, evaluate the following:

sec 29°cosec 61°+2 cot 8° cot 17° cot 45° cot 73° cot 82°3 (sin238°+sin252°)\dfrac{\text{sec 29°}}{\text{cosec 61°}} + \text{2 cot 8° cot 17° cot 45° cot 73° cot 82°} - \text{3 (sin}^2 38° + \text{sin}^2 52°).

Trigonometrical Ratios

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Answer

Solving,

sec 29°cosec 61°+2 cot 8° cot 17° cot 45° cot 73° cot 82°3 (sin238°+sin252°)sec 29°cosec (90° - 29°)+2 cot (90° - 82°) cot (90° - 73°) cot 45° cot 73° cot 82°3 (sin238°+sin2(90°38°))As, cosec(90° - θ) = sec θ, cot(90° - θ) = tan θsec 29°sec 29°+2 tan 82° tan 73° cot 45°×1tan 73°×1tan 82°3 (sin238°+cos238°)As, sin2θ+cos2θ=11+2 cot 45°31+230.\Rightarrow \dfrac{\text{sec 29°}}{\text{cosec 61°}} + \text{2 cot 8° cot 17° cot 45° cot 73° cot 82°} - \text{3 (sin}^2 38° + \text{sin}^2 52°) \\[1em] \Rightarrow \dfrac{\text{sec 29°}}{\text{cosec (90° - 29°)}} + \text{2 cot (90° - 82°) cot (90° - 73°) cot 45° cot 73° cot 82°} - \text{3 (sin}^2 38° + \text{sin}^2 (90° - 38°)) \\[1em] \text{As, cosec(90° - θ) = sec θ, cot(90° - θ) = tan θ} \\[1em] \Rightarrow \dfrac{\text{sec 29°}}{\text{sec 29°}} + \text{2 tan 82° tan 73° cot 45°} \times \dfrac{1}{\text{tan 73°}} \times \dfrac{1}{\text{tan 82°}} - \text{3 (sin}^2 38° + \text{cos}^2 38°) \\[1em] \text{As, sin}^2 θ + \text{cos}^2 θ = 1 \\[1em] \Rightarrow 1 + \text{2 cot 45°} - 3 \\[1em] \Rightarrow 1 + 2 - 3 \\[1em] \Rightarrow 0.

Hence, sec 29°cosec 61°+2 cot 8° cot 17° cot 45° cot 73° cot 82°3 (sin238°+sin252°)\dfrac{\text{sec 29°}}{\text{cosec 61°}} + \text{2 cot 8° cot 17° cot 45° cot 73° cot 82°} - \text{3 (sin}^2 38° + \text{sin}^2 52°) = 0.

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