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We can write C = 9 0 ° − A , h cos A = 9 cos 2 A , h sin A = 8 2 cos ( 4 5 ° − 2 A ) , where h = ∣ A C ∣
⟹ 8 ( cos 2 A + sin 2 A ) = h sin A
⟹ h 2 = sin 2 A 6 4 ( 1 + sin A ) = 2 cos 2 A 8 1 ( 1 + cos A )
⟹ sin A = 1 2 8 cos 2 A 8 1 + 8 1 cos A − 2 0 9 cos 2 A − 8 1 cos 3 A
Squaring, converting into cosine function only and solving we get
cos A = 5 3 , sin A = 5 4 , h 2 = 1 8 0 .
So, h = ∣ A C ∣ = 1 8 0 ≈ 1 3 . 4 1 6 4 .
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Let A C = x and ∠ C = θ . Then we have:
B C : x cos θ A B : x sin θ B C A B : tan θ 1 − t 2 3 2 t 3 2 t 9 t 3 + 9 t 2 + 2 3 t − 9 ⟹ t B C : x ⋅ 5 4 ⟹ x = 8 2 cos 2 θ = 9 cos ( 4 5 ∘ − 2 θ ) = 2 9 ( cos 2 θ + sin 2 θ ) = 1 6 cos 2 θ 9 ( cos 2 θ + sin 2 θ ) = 1 6 9 ( 1 + tan 2 θ ) = 9 ( 1 + t ) = 9 ( 1 + t − t 2 − t 3 ) = 0 = tan 2 θ = 3 1 = 8 2 ⋅ 1 0 3 = 3 2 0 ≈ 1 3 . 4 Let t = tan 2 θ ⟹ cos 2 θ = 1 0 3 ⟹ cos θ = 2 ( 1 0 3 ) 2 − 1 = 5 4