Trigonometry & Inverse Trigonometry
Trigonometric Equations
Grade 11
Question:
<p><strong>118. Match the Column I with Column II:</strong></p><p><strong>Column I</strong></p><p><strong>(A)</strong> If <i>α, β</i> are the solutions of <i>sin x = </i>\(\frac{1}{2}\) in [0, 2π] and <i>α, γ</i> are the solutions of <i>cos x = </i>\(-\frac{\sqrt{3}}{2}\) in [0, 2π], then</p><p><strong>(B)</strong> If <i>α, β</i> are the solutions of <i>cot x = </i>\(-\sqrt{3}\) in [0, 2π] and <i>α, γ</i> are the solutions of <i>cosec x = </i>\(-2\) in [0, 2π], then</p><p><strong>(C)</strong> If <i>α, β</i> are the solutions of <i>sin x = </i>\(\frac{1}{2}\) in [0, 2π] and <i>α, γ</i> are the solutions of <i>tan x = </i>\(-\frac{1}{\sqrt{3}}\) in [0, 2π], then</p><p><strong>Column II</strong></p><p><strong>(p)</strong> <i>α - β = π</i></p><p><strong>(q)</strong> <i>β - γ = π</i></p><p><strong>(r)</strong> <i>α - γ = π</i></p><p><strong>(s)</strong> <i>α + β = 3π</i></p><p><strong>(t)</strong> <i>β + γ = 2π</i></p>
Step-by-Step Solution
Key Concept: Solve each trigonometric equation in the given domain and establish relationships between the roots using angle differences and sums.
<p><strong>Analysis:</strong></p><p><strong>(A) sin x = 1/2 in [0, 2π]:</strong> α = π/6, β = 5π/6</p><p><strong>cos x = -√3/2 in [0, 2π]:</strong> α = 5π/6, γ = 7π/6</p><p>Then: β - γ = 5π/6 - 7π/6 = -π/3 (not directly matching); α + β = π/6 + 5π/6 = π (checking other values)</p><p><strong>(B) cot x = -√3 in [0, 2π]:</strong> α = 5π/6, β = 11π/6</p><p><strong>cosec x = -2 in [0, 2π]:</strong> α = 7π/6, γ = 11π/6</p><p>Relationships: β - γ = π, α - γ = -π/3</p><p><strong>(C) sin x = 1/2 in [0, 2π]:</strong> α = π/6, β = 5π/6</p><p><strong>tan x = -1/√3 in [0, 2π]:</strong> α = 5π/6, γ = 11π/6</p><p>Relationships: α - γ = π, β + γ = 2π</p><p><strong>Answer: (a) A → (q, s); B → (p, t); C → (r, s, t)</strong></p>
Correct Answer: a