Question

OAB is a quadrant of a circle. The radius OA =3.5 cm and OD =2cm. Calculate the area of shaded portion .

Answer 1

use the area of 1/4 circle - area of triangle to find the shaded region
  
area of quadrant =1/4πr^2                              area of triangle= 1/2 b*h
                             = 1/4 *  π * 3.5^2                                            =1/2 * 3.5*2
                              = 9.62 cm^2                                                   = 3.5cm^2
           

Area of quadrant - area of triangle  
9.62 - 3.5
answer= 6.12 cm^2

Answer 2

Step-by-step explanation:

In the figure alongside, OAB is a quadrant of a circle. The radius OA=3.5 cm and OD=2 cm. Calculate the area of the shaded portion. (Takeπ=

7

22

Radius of quadrant OACB,r=3.5 cm

∴ Area of quadrant OACB=

4

1

πr

2

=

4

1

×

7

22

×3.5×3.5=9.625 cm

2

Here, ∠AOD=90

∘

Then area of ΔAOD=

2

1

× base × height$$

Base =3.5 cm and height =2 cm

∴=

2

1

×3.5×2=3.5 cm

2

Area of shaded portion = Area of quadrant − Area of triangle

=9.625−3.5

=6.125 cm

2

.