In figure find the area of the red part.

Step-by-step explanation:

Given : A rectangle 4 x 8 , a semicircle

Diagonal intersecting semicircle  

To Find :Area of red part

Angle AC make AB   α = ∠BAC

tan α = BC/AB = 4/8 = 1/2

=> α = 26.565°

∠ECA = ∠BAC = α

EC = EF = 4

=> ∠CEF = 180° - 2α

∠AED = 45°  as   AE is  diagonal of Square of side  4

=> ∠AEF  + 180° - 2α + 45° = 180°

=>  ∠AEF =  2α - 45°  = 8.13°

in Left side area  between square  and circle is split in 2 Equal parts

(1/2) area - area AFG = area of Red part

in Left side area  between square  and circle  = 4² - (1/4)π4²

= 3.4336 sq unit

half  =  1.7168 sq unit  

Now find area AFG = area ΔAEF - sector EGF

area ΔAEF  

AE = 4√2  , EF = 4    angle = 8.13°

area ΔAEF   = (1/2) 4√2 * 4 sin 8.13° = 1.6 sq unit

area  sector EGF  = (8.13/360)π4² = 1.135  sq unit

area AFG  = 1.6 - 1.135  = 0.465 sq unit

Area of Red part = 1.7168 - 0.465 sq unit

= 1.2518 sq unit

= 1.252  sq unit

= 1.25 sq unit.

Hope this helps!!

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