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If sin (30° – θ) = cos (60° + ϕ), then (a) ϕ – θ = 30° (b) ϕ – θ = 0° (c) ϕ + θ = 60° (d) ϕ – θ = 60° |
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Answer» (b) θ – ϕ = 0 sin (30° – θ) = cos (60° + ϕ) ⇒ cos (90° – (30° – θ) = cos (60° + ϕ) (∵ sin θ = cos (90° – θ)) ⇒ cos (60° + θ) = cos (60° + ϕ) ⇒ 60° + θ = 60° + ϕ ⇒ θ – ϕ = 0. |
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