In the above Oblique Cylinder , is a parallelogram and is a right triangle.
Let the volume and the lateral surface area of the Oblique Cylinder be and respectively, where is a positive real number.
(1): Find the restriction on for which the radius minimizes the distance .
(2): Find in degrees.
If and , find + .
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V = π r 2 H = b 2 ⟹ H = π r 2 b 2 and A = 2 π r s = b ⟹ s = 2 π r b
⟹ Y ( r ) = y 2 ( r ) = s 2 ( r ) − H 2 ( r ) = π 2 b 2 ( 4 r 2 1 − r 4 b 2 ) ⟹ d r d Y = π 2 b 2 ( 2 r 5 8 b 2 − r 2 ) r > 0 ⟹ r = 2 2 b ⟹ s = 4 2 π 1 and H = 8 π 1 and y = s 2 − H 2 = 8 π 1 = H .
For r to minimize the distance y d r 2 d 2 Y ∣ r = 2 2 b > 0 ⟹ d r 2 d 2 Y ∣ r = 2 2 b = 1 2 8 π 2 1 ( 3 − 5 b ) > 0 ⟹ b < 5 3 ⟹ r < 5 6 2 = α ≈ 1 . 6 9 7 0 5 6 .
Let m ∠ P T R = λ ⟹ cos ( λ ) = s ( r ) y ( r ) = 2 1 and θ = 1 8 0 − λ ⟹ cos ( θ ) = cos ( 1 8 0 − θ ) = − cos ( λ ) = − 2 1 ⟹ θ = 1 3 5 ∘
⟹ d 2 = s 2 + 4 r 2 + 4 r s cos ( λ ) = 3 2 π 2 1 + 3 2 b 2 + π 2 b < 3 2 π 2 1 + 3 2 ( 2 5 9 ) + π 2 ( 5 3 ) =
2 ( 2 0 π ) 2 ( 9 6 π ) 2 + 4 8 0 2 π + 2 5 ⟹ d < 2 0 2 π ( 9 6 π ) 2 + 4 8 0 2 π + 2 5 = β ≈ 3 . 4 3 4 1 3
∴ ⌊ α ⌋ + ⌊ β ⌋ + θ = 1 3 9