simplify :
,0° < θ < 90°
Show answer & explanation
Correct answer: B
Explanation
The correct answer is option 2 i.e. 1
(Sinθ + secθ)2 + (Cosθ + Cosecθ)2/(1 + secθcosecθ)2
1/Sinθ = Cosecθ
1/Cosθ = Secθ
Sin2θ + Cos2θ = 1
(A + B)2 = A2 + 2AB + B2
(Sinθ + secθ)2 + (Cosθ + Cosecθ)2
= (Sinθ + 1/Cosθ)2 + (Cosθ + 1/Sinθ)2
= Sin2θ + 2 × Sinθ × (1/Cosθ) + 1/Cos2θ + Cos2θ + 2 × Cosθ × (1/Sinθ) + 1/Sin2θ
= (Sin2θ + Cos2θ) + {(2Sinθ/Cosθ) + (2Cosθ Sinθ)} + (1/Cos2θ + 1/Sin2θ)
= 1 + {2/(Cosθ × Sinθ)} + {1/(Cos2θ × Sin2θ)}
= (1 + 2 × Secθ × Cosecθ + Sec2θ × Cosec2θ)
= (1 + SecθCosecθ)2
(Sinθ + secθ)2 + (Cosθ + Cosecθ)2/(1 + secθcosecθ)2
= (1 + SecθCosecθ)2/(1 + SecθCosecθ)2
= 1