Sketch the region common to the circlex2+y2=25and the parabola y2=8x. Also, find the area of the region, using integration.

Given the boundaries of the area to be found are,


• the circle, x2 + y2 = 25 ---(1)


• the parabola, y2 = 8x ---- (2)


From the equation, of the first circle, x2 + y2 = 25


• the vertex at (0,0) i.e. the origin


• the radius is 5 units.


From the equation, of the parabola , y2 = 8x


• the vertex at (0,0) i.e. the origin


• Symmetric about the x-axis, as it has the even power of y.


Now to find the point of intersection of (1) and (2), substitute y2 = 8x in (1)


x2 + 8x = 25


x2 + 8x - 25= 0



as y cannot be imaginary, we reject the negative value of x


so


So the two points, A and B are the points where (1) and (2) meet.


The line AB meets the x-axis at D = [(√41 -4),0]


Substitute y = 0 in (1),


x2 + 0 = 25


x = ±5


So the circle intersects the x-axis at C(5,0)and E(-5,0)



As x and y have even powers for the circle, they will be symmetrical about the x-axis and y-axis.


Consider the circle, x2 + y2 = 25, can be re-written as



----- (3)


Consider the parabola, y2 = 8x, can be re-written as


----- (4)


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 OADO+ Area of DACD


Area of OCAOis




[Using the formula, and ]


Let √41 – 4 = a




[sin-1(1) = 90° and sin-1(0) = 0°]




The Area of OCAOsq. units, where a = √41 - 4


Now substituting the area of OCAOin equation (5)


Area of OACBO= 2 × Area of OCAO




Area of the required region is sq. units, where a = √41 - 4


1