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.
(1): Find the value of the radius which maximizes the distance .
(2): Find the distance and find (in degrees).
Express the answer as .
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V = π r 2 H = 1 ⟹ H = π r 2 1 and A = 2 π r s = 1 ⟹ s = 2 π r 1
⟹ Y ( r ) = y 2 ( r ) = s 2 ( r ) − H 2 ( r ) = 4 π 2 r 2 1 − π 2 r 4 1 ⟹ d r d Y = π 2 1 ( 2 r 5 8 − r 2 ) r > 0 ⟹ r = 2 2 ⟹ s = 4 2 π 1 and H = 8 π 1 and y = s 2 − H 2 = 8 π 1 = H .
d r 2 d 2 Y ∣ r = 2 2 = ( 8 π ) 2 − 1 < 0 ⟹ max at r = 2 2 .
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 + π 2 = 3 2 π 2 3 2 2 π 2 + 3 2 2 π + 1 ⟹ d = 4 2 π 3 2 2 π 2 + 3 2 2 π + 1 ≈ 5 . 6 9 6 7 8
∴ ⌊ d + θ ⌋ = 1 4 0