A rectangle whose length and breadth are 12 cm and 5 cm respectively is inscribed in a circle. Find the area of the blue coloured region, as shown in the figure 13.19.
Figure 13.19
given length (l) = 12 cm
breadth (b) = 5 cm
we can notice from the fig. that the Hypotenuse of ADB is same as diameter of the circle.
from the triangle ABD
BD2 = AD2 + AB2
BD = √(52 + 122)
(∵ AD is breadth, AB is length of the rectangle)
BD = √(25 + 144)
= √169
= 13 cm
∴ diameter of the circle = 13 cm
Radius of the circle (r) = 6.5 cm
Area of the shade region = Area of circle – area of rectangle
= π r2 – b × h
= π × 6.52 – 5 × 12
= 72.732 cm2