A Very Nice Geometry Problem | You should be able to solve this!
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- Опубліковано 3 лип 2024
- A Very Nice Geometry Problem | You should be able to solve this!
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2(2R-2)=(4)(4)
4R-4=16
4R=20
So R=5
OD=5-2=3; OC=5
tan(DOC)=4/3=53.13°
π(5^2)(53.13°/360°=11.6
Shaded area=11.6-1/2(4)(3)=5.60.❤❤❤
I thought some exciting things will happen for finding the shaded region but in the end sin inverse destroyrd all my excitement.
Let the circle with diameter AB. (construction)
Extend the line segment CD that intersects the circle at point P. ( construction)
Now we must calculate the area of the circular sector with center O and arc PC , subtract the area of the triangle OPC and then divide by 2 .
*We need only to estimate the angle < POC , but we can’t do it using Geometry !!!!!!*
In Geometry , if we only have relations between straight segments then the requested angle will be 30°,36°,45°,60°, 72°, 90°,120°, 150° ....... finish
Intersecting chords theorem:
(2R-2).2 = 4²
4R - 4 = 16
R = 5 cm
tan α = 4/(R-2) = 4/3
α = 53,13°
A = ¼ R² (2α - sin 2α)
A = ¼ 5² (106,26°- sin 106,26°)
A = 5,59 cm² ( Solved √ )
OD = x
R is the radius
Now
(R-x )*(R +x )=16
Geometric mean theorem
R-x =2
R+x=8
R=5
It is for derivation of radius
(2)^A/O2/Coso° =4A/O/Tano° (4)^2A/O/Tano° =16A/O/Tano° {4A/OCoso°+16A/O/Tano°} =20A/O/Coso°Tano° 180°/20A/O/Coso°Tano°=9 A/O/Coso°Tano° {A/O/Coso°Tano° ➖ 9A/O/Coso°Tano°+9)
4^2+(R-2)^2=R^2...R=5...πR^2:2π=As:(arctg3/4+π/2)...As=(arctg3/4+π/2)25/2..Ablue=(25π)/2-As-4*3/2=5,5911..
AD:CD=CD:BD 2:4=4:8 8+2=10=AB 10/2=5 R
Draw radius OC. As OC = OA = r and DA = 2, OD = r-2.
Triangle ∆CDO:
OD² + CD² = OC²
(r-2)² + 4² = r²
r² - 4r + 4 + 16 = r²
4r = 20
r = 5
The red shaded area is equal to the area of the sector subtended by minor arc AC minus the area of ∆CDO. Let ∠AOC = θ. θ = sin⁻¹(4/5) ≈ 53.13°.
Red shaded area:
Aᵣ = (θ/360°)πr² - OD(CD)/2
Aᵣ = (sin⁻¹(4/5)/360°)π(5)² - (5-2)(4)/2
Aᵣ = (sin⁻¹(4/5)/360°)π(25) - 3(2)
Aᵣ = 5sin⁻¹(4/5)π/72 - 6 ≈ 5.59 sq units
Given the title and my previous exposure to rats and angles, this seems easy.
we call sin inverse: arcsin.
I smelled this coming! No exact answer! Resort to numerical result!
This type of exercise should be do e without calculator…so dumbs downs to you
❤❤❤❤❤❤❤❤🎉🎉😊😊😊😊❤❤🎉🎉🎉🎉