Sketch the region common to the circle x2+y2=16 and the parabola x2=6y. Also, find the area of the region, using integration.
Given the boundaries of the area to be found are,
• the circle, x2 + y2 = 16 ---(1)
• the parabola, x2 = 6y ---- (2)
From the equation, of the first circle, x2 + y2 = 16
• the vertex at (0,0) i.e. the origin
• the radius is 4 unit.
From the equation, parabola, x2 = 6y
• the vertex at (0,0) i.e. the origin
• Symmetric about the y-axis, as it has the even power of x.
Now to find the point of intersection of (1) and (2), substitute x2 = 6y in (1)
6y + y2 = 16
y2 + 6y - 16= 0
y = 2 (or) y = -8
as x cannot be imaginary, y = 2
Substituting x in (2), we get x = ± 2√3
So the two points, A and B where (1) and (2) meet are A = (2√3,2) and B = (-2√3,2)
As x and y have even powers for both the circle and parabola, they will be symmetrical about the x-axis and y-axis.
Consider the circle, x2 + y2 = 16, can be re-written as
----- (3)
Consider the parabola, x2 = 6y, can be re-written as
----- (4)
Let us drop a perpendicular from A on to x-axis. The base of the perpendicular is D = (2√ 3, 0)
Now, the area to be found will be the area is
Area of the required region = Area of OACBO.
Area of OABCO= Area of OCAO+ Area of OCBO
[area of OCBO= area of OCAOas the circle is symmetrical about the y-axis]
Area of OACBO= 2 × Area of OCAO---- (5)
Area of OCAO= Area of OCAD - Area of OADO
Area of OCAOis
[Using the formula, and ]
[sin-1(1) = 90° and ]
The Area of OCAOsq. units
Now substituting the area of OCAOin equation (5)
Area of OACBO= 2 × Area of OCAO
Area of the required region is sq. units.