The formula for the area of a sector of a circle is:

We want to find the area of the blue sector.
First, let's find the angle of the sector. This angle and angle 84 are in a straight line. Thus, we can say:

Where θ is the angle of the sector.
Let's solve for θ:

We also recognize that BD is the diameter and BA is the radius.
We know
Radius is HALF of Diameter.
Given,
Diameter = 6
Radius = 6/2 = 3
Now, let's calculate the area of the sector:

Rounded to 2 decimal places,
Answer
Area = 7.54 sq. cm.