Given that , find the minimum value of
Hint: It's on the draft paper of a geometry problem.
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Let us draw a triangle △ A B C with ∣ A B ∣ = 3 , ∣ A C ∣ = 6 , ∠ B A C = x . Then ∣ B C ∣ = 3 5 − 4 cos x . Let us draw a line A D perpendicular to A C such that ∣ A D ∣ = 2 . Join B D . Then ∣ B D ∣ = 1 3 − 1 2 sin x . The minimum of ∣ B D ∣ + ∣ B C ∣ is ∣ C D ∣ = 6 2 + 2 2 = 4 0 , so that the required minimum is 4 0 .