In the above diagram square is tangent to the circle at point and vertices and are on the circle.
Let be the area of the red regions. If and are the smallest coprime positive integers such that , where , , , , and are coprime positive integers, find .
This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try
refreshing the page, (b) enabling javascript if it is disabled on your browser and,
finally, (c)
loading the
non-javascript version of this page
. We're sorry about the hassle.
Let a be a side of square A B C D .
△ C O D is an isosceles triangle ⟹ O Q is the perpendicular bisector of base C D ⟹
C Q = Q D = 2 a
In right △ C O Q we have r 2 = a 2 − 2 a r + r 2 + 4 a 2 ⟹ a ( 5 a − 8 r ) = 0
and a = 0 ⟹ r = 8 5 a
B M = a − 2 ( a − r ) = 2 r − a = 4 a and sin ( θ ) = 2 r a = 5 4 ⟹
Area of sector M O P is A s = 2 1 θ r 2 = 2 1 arcsin ( 5 4 ) ( 6 4 2 5 ) a 2 = 1 2 8 2 5 arcsin ( 5 4 ) a 2
and
Area of trapezoid P B M O is A P B M O = 2 1 ( r + B M ) ( 2 a ) = 2 1 ( 8 5 a + 4 a ) ( 2 a ) = 3 2 7 a 2
⟹ A g r e e n = 2 ( A P B M O − A s ) = 2 ( 3 2 7 − 1 2 8 2 5 arcsin ( 5 4 ) ) a 2 =
( 6 4 2 8 − 2 5 arcsin ( 5 4 ) ) a 2
In △ M O C we have sin ( θ ∗ ) = r a − r = 5 3 ⟹ θ ∗ = arcsin ( 5 3 ) ⟹
2 θ ∗ = 2 arcsin ( 5 3 ) ⟹ area of sector M O C is A s ∗ = 2 1 ( 2 θ ) r 2 = 6 4 2 5 arcsin ( 4 3 ) a 2
and A △ M O C = 2 1 ( 2 ( a − r ) ) ( 2 a ) = ( 8 3 a ) ( 2 a ) = 1 6 3 a 2
⟹ A b l u e = 2 ( A s ∗ − A △ M O C ) = 6 4 5 0 arcsin ( 5 3 ) − 2 4 a 2
From above A s = 1 2 8 2 5 arcsin ( 5 4 ) a 2 and A △ C O R = 2 1 ( a − r ) ( 2 a ) = 2 1 ( 8 3 a ) ( 2 a ) =
3 2 3 a 2 ⟹ A p u r p l e = 2 ( A s − A △ C O R ) = 6 4 2 5 arcsin ( 5 4 ) − 1 2 a 2 ⟹
A A B C D A = A A B C D A g r e e n + A b l u e + A p u r p l e = 3 2 2 5 arcsin ( 5 3 ) − 4 = p α arcsin ( ω λ ) − β ⟹
α + β + λ + ω + p = 6 9 .
Below is an alternative approach:
From above A s = 1 2 8 2 5 arcsin ( 5 4 ) a 2 ⟹ 2 A s = 6 4 2 5 arcsin ( 5 4 ) a 2
and A △ M O N = 2 1 ( a ) ( a − r ) = 2 1 ( 8 3 ) a 2 = 1 6 3 a 2
⟹ Area of segment is M P N is A s ∗ = 2 A s − A △ M O N = 6 4 2 5 arcsin ( 5 4 ) − 1 2 a 2
A w h i t e = A M C N D + A s ∗ = 2 ( 8 3 ) a 2 + A s ∗ = ( 4 3 + 6 4 2 5 arcsin ( 5 4 ) − 1 2 ) a 2 =
6 4 3 6 + 2 5 arcsin ( 5 4 ) a 2 ⟹ A T = 6 4 2 5 π a 2 − A w h i t e = 6 4 2 5 π − 2 5 arcsin ( 5 4 ) − 3 6 a 2
Form above A g r e e n = 6 4 2 8 − 2 5 arcsin ( 5 4 ) a 2 ⟹
A = A T + A g r e e n = 6 4 2 5 π − 5 0 arcsin ( 5 4 ) − 8 a 2
Letting θ ∗ ∗ = arcsin ( 5 3 ) ⟹ A = 6 4 2 5 π − 5 0 ( 2 π − θ ∗ ∗ ) − 8 a 2 =
3 2 2 5 arcsin ( 5 3 ) − 4 a 2 ⟹ A A B C D A = 3 2 2 5 arcsin ( 5 3 ) − 4 = p α arcsin ( ω λ ) − β
⟹ α + β + λ + ω + p = 6 9 .