Trigonometry
-  If tan θ = 1, then the value of 8sin θ + 5cos θ is sin3θ - 2cos3θ + 7cos θ 
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                        View Hint View Answer Discuss in Forum tanθ = 1 
 ⇒ θ = 45°∴ 8 sin θ + 5 cos θ sin3θ - 2cos3θ + 7 cosθ  
 Correct Option: Atanθ = 1 
 ⇒ θ = 45°∴ 8 sin θ + 5 cos θ sin3θ - 2cos3θ + 7 cosθ  
 
-  If tan θ = 1, then the value of 8sin θ + 5cos θ is sin3θ - 2cos3θ + 7cos θ 
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                        View Hint View Answer Discuss in Forum tanθ = 1 
 ⇒ θ = 45°∴ 8 sin θ + 5 cos θ sin3θ - 2cos3θ + 7 cosθ  
 Correct Option: Atanθ = 1 
 ⇒ θ = 45°∴ 8 sin θ + 5 cos θ sin3θ - 2cos3θ + 7 cosθ  
 
-  If sin α sec (30° + α) = 1 (0 < a < 60°), then the value of sin α + cos 2α is
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                        View Hint View Answer Discuss in Forum sinα = 1 cos(30° + α) ⇒ sinα = 1 sin(90° - 30 - α) ⇒ sinα = 1 sin(60° - α) 
 ⇒ sin α = sin (60° – α)
 ⇒ 2α = 60° ⇒ α = 30°
 ∴ sinα + cos 2α
 = sin 30° + cos 60°= 1 + 1 = 1 2 2 
 Correct Option: Asinα = 1 cos(30° + α) ⇒ sinα = 1 sin(90° - 30 - α) ⇒ sinα = 1 sin(60° - α) 
 ⇒ sin α = sin (60° – α)
 ⇒ 2α = 60° ⇒ α = 30°
 ∴ sinα + cos 2α
 = sin 30° + cos 60°= 1 + 1 = 1 2 2 
 
-  If cos4 θ – sin4 θ = (2 / 3) , then the value of 2 cos²θ– 1 is
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                        View Hint View Answer Discuss in Forum cos4 θ - sin4 θ = 2 3 (cos2 θ + sin2 θ) (cos2 θ – sin2 θ) 2 3 ⇒ cos2 θ - sin2 θ 2 3 ⇒ 2cos2 θ - 1 2 3 
 Correct Option: Ccos4 θ - sin4 θ = 2 3 (cos2 θ + sin2 θ) (cos2 θ – sin2 θ) 2 3 ⇒ cos2 θ - sin2 θ 2 3 ⇒ 2cos2 θ - 1 2 3 
 
-  If sin α + cos β = 2 (0° ≤ β ≤ α ≤ 90°), then sin (2α + β / 3) =
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                        View Hint View Answer Discuss in Forum sinα + cosβ = 2 
 sinα ≤ 1 ; cosβ ≤ 1
 ⇒ α = 90° ; β = 0° = sin 60° = √3 2 
 Also,cos α = cos 30° = √3 3 2 
 Correct Option: Bsinα + cosβ = 2 
 sinα ≤ 1 ; cosβ ≤ 1
 ⇒ α = 90° ; β = 0° = sin 60° = √3 2 
 Also,cos α = cos 30° = √3 3 2 
 
 
	