In the above diagram, the ellipse goes thru the points and the hyperbola goes thru the points .
Find the area of the region bounded by the hyperbola and the ellipse above to five decimal places.
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Using a x 2 + b x y + c y 2 + d x + e y = 0 and the points I chose above to generate the ellipse.
(1) ( 0 , − 4 ) : 4 c − e = 0 ⟹ c = 4 e
(2) ( 8 , 4 ) : 1 6 a + 8 b + 4 c + 2 d + e = 0
(3) ( 8 , − 4 ) : 1 6 a − 8 b + 4 c + 2 d − e = 0
Subtracting (3) from (2) we obtain: 8 b + e = 0 ⟹ b = − 8 e
(4) ( 5 , 8 ) : 2 5 a + 4 0 b + 6 4 c + 5 d + 8 c = 0
Replacing c = 4 e and b = − 8 e into (2) and (4) ⟹
1 6 a + 2 d = − e
2 5 a + 5 d = − 1 9 e
⟹ a = 1 0 1 1 e and d = − 1 0 9 3 e
⟹ 1 0 1 1 x 2 − 8 1 x y + 4 1 y 2 − 1 0 9 3 x + y = 0 ⟹ 4 4 x 2 − 5 x y + 1 0 y 2 − 3 7 2 x + 4 0 y = 0 ⟹ 1 0 y 2 + 5 ( x − 8 ) y + 4 4 x 2 − 3 7 2 x = 0
Solving for y we obtain:
y = 4 x − 8 ± 2 0 1 3 4 7 5 2 2 0 7 7 4 4 − ( 3 4 7 x − 1 4 4 8 ) 2 .
y e ( x ) = 4 x − 8 − 2 0 1 3 4 7 5 2 2 0 7 7 4 4 − ( 3 4 7 x − 1 4 4 8 ) 2 for the portion of the ellipse below the line y = 4 x − 8 .
Using x 2 + B x y + C y 2 + D x + E y + F = 0 and the points I chose above to generate the hyperbola.
(1) ( 0 , − 4 ) : 1 6 C − 4 E + F = 0 ⟹ F = 4 E − 1 6 C
(2) ( 8 , − 4 ) : 4 B − D = 8 ⟹ D = 4 B − 8 .
Using (1) and (2) above ⟹
(3): ( − 4 , − 8 ) : 4 B + 1 2 C − E = − 1 2
(4) ( 1 2 , − 8 ) : − 1 2 B + 1 2 C − E = − 1 2
(5) ( 4 , − 2 ) : 4 B − 6 C + E = 8
(3) + (5) ⟹ 4 B + 3 C = − 2
(3) - (4) ⟹ B = 0 ⟹ C = − 3 2 ⟹ D = − 8 ⟹ E = 4 ⟹ F = 3 8 0
⟹ 3 x 2 − 2 y 2 − 2 4 x + 1 2 y = − 8 0 ⟹ − 3 x 2 + 2 y 2 + 2 4 x − 1 2 y = 8 0 ⟹
2 ( y − 3 ) 2 − 3 ( x − 4 ) 2 = 5 0
Using the given portion of hyperbola below the line 4 x − 8 ⟹ y h ( x ) = 3 − 2 1 ( 5 0 + 3 ( x − 4 ) 3 ⟹ A h = ∫ 0 8 y h ( x ) d x .
For I ( x ) = 2 1 ∫ 5 0 + 3 ( x − 4 ) 2
Let 3 ( x − 4 ) = 5 0 tan ( θ ) ⟹ d x = 3 5 0 sec 2 ( θ ) d θ ⟹ I ( θ ) = 6 5 0 ∫ sec 3 ( θ ) d θ
For ∫ sec 3 ( θ ) d θ
Let u = sec ( θ ) ⟹ d u = sec ( θ ) tan ( θ ) and d v = sec 2 ( θ ) ⟹ v = tan ( θ ) ⟹ ∫ sec 3 ( θ ) d θ = sec ( θ ) tan ( θ ) − ∫ sec ( θ ) + ∫ sec ( θ ) d θ ⟹ ( ∫ sec 3 ( θ ) d θ = 2 1 ( sec ( θ ) tan ( θ ) + ln ∣ sec ( θ ) + tan ( θ ) ∣ ) ⟹
I ( x ) ∣ 0 8 = 6 2 5 ( 5 0 5 0 + 3 ( x − 4 ) 2 3 ( x − 4 ) + ln ∣ 5 0 5 0 + 3 ( x − 4 ) 2 + 3 ( x − 4 ) ∣ ) ∣ 0 8 = 2 8 + 6 2 5 ln ( 7 2 − 4 3 7 2 + 4 3 )
⟹ A h = − 4 − 6 2 5 ln ( 7 2 − 4 3 7 2 + 4 3 ) ≈ − 2 1 . 6 9 7 8 6
The area of the ellipse is A e = ∫ 0 8 y e ( x ) d x .
A e = 2 0 1 3 4 7 5 ∫ 0 8 − 2 2 0 7 7 4 4 − ( 3 4 7 x − 1 4 4 8 ) 2 + 4 x − 8 d x = 4 5 3 4 7 1 ∫ 0 8 − 2 2 0 7 7 4 4 − ( 3 4 7 x − 1 4 4 8 ) 2 + 4 x − 8 d x .
For I ( x ) = ∫ 2 2 0 7 7 4 4 − ( 3 4 7 x − 1 4 4 8 ) 2 d x
Let 3 4 7 x − 1 4 4 8 = 2 2 0 7 7 4 4 sin ( θ ) ⟹ d x = 3 4 7 2 2 0 7 7 4 4 cos ( θ )
⟹ I ( θ ) = 3 4 7 2 2 0 7 7 4 4 ∫ cos 2 ( θ ) d θ = 6 9 4 2 2 0 7 7 4 4 ∫ ( 1 + cos ( 2 θ ) ) d θ = 6 9 4 2 2 0 7 7 4 4 ( θ + sin ( θ ) cos ( θ ) )
⟹ I ( x ) = 6 9 4 2 2 0 7 7 4 4 ( arcsin ( 2 2 0 7 7 4 4 3 4 7 x − 1 4 4 8 ) + 2 2 0 7 7 4 4 3 4 7 x − 1 4 4 8 2 2 0 7 7 4 4 − ( 3 4 7 x − 1 4 4 8 ) 2 ) ⟹
A e = − ( 3 4 7 ) 2 3 5 2 7 5 9 6 8 ( arcsin ( 2 2 0 7 7 4 4 3 4 7 x − 1 4 4 8 ) + 2 2 0 7 7 4 4 3 4 7 x − 1 4 4 8 2 2 0 7 7 4 4 − ( 3 4 7 x − 1 4 4 8 ) 2 ) ∣ 0 8 =
− ( 3 4 7 ) 2 3 5 2 7 5 9 6 8 ( arcsin ( 2 2 0 7 7 4 4 1 3 2 8 ) + arcsin ( 2 2 0 7 7 4 4 1 4 4 8 ) + 2 2 0 7 7 4 4 1 3 2 8 4 4 4 1 6 0 + 2 2 0 7 7 4 4 1 4 4 8 1 1 1 0 4 0 ) − 8 =
− ( 3 4 7 ) 2 3 5 2 7 5 9 6 8 ( arcsin ( 2 8 1 1 8 3 ) + arcsin ( 5 6 1 1 1 8 1 ) + 3 4 4 9 6 5 1 3 1 7 3 5 ) − 8 ≈ − 6 6 . 9 1 2 9 5
⟹ A = ∫ 0 8 y h ( x ) − y e ( x ) d x = A h − A e = 4 4 . 9 1 2 9 5 .