An integer is called a perfect square if it is square of another integer. The number of perfect square points (i.e. both coordinates are perfect squares that lie exactly within the circle
$$(x - 12)^2 + (y - 10)^2 = 64$$ is
The given equation is $$(x - 12)^2 + (y - 10)^2 = 64$$
$$(x - 12)^2 + (y - 10)^2 = 8^2$$
It is an equation of a circle with a radius of 8 units & its centre is at (12,10).
It implies that the extreme coordinate of 'x' is = 12+8 = 20.
Similarly, the extreme coordinate of 'y' is = 10+8 = 18.
The square numbers which are less than 20 & 18 are 4, 9 & 16.
For a point (x,y) to lie inside the circle, $$(x - 12)^2 + (y - 10)^2 = 64$$, the value of $$(x - 12)^2 + (y - 10)^2$$ should be less than 64.
Case (i):- (4,4)
$$(4-12)^2+(4-10)^2=8^2+6^2=100 > 64$$.
Hence, the point lies outside the circle.
As $$(4-12)^2=64$$, all the square points with '4' as x coordinate i.e (4,9), (4,16), lie outside the circle.
Case (ii):- (9,9)
$$(9-12)^2+(9-10)^2=3^2+1^2=10 < 64$$.
Hence, the point lies inside the circle.
Case (iii):- (16,16)
$$(16-12)^2+(16-10)^2=4^2+6^2=52 < 64$$.
Hence, the point lies inside the circle.
Case (iv):- (9,4)
$$(9-12)^2+(4-10)^2=3^2+6^2=45 < 64$$.
Hence, the point lies inside the circle.
Case (v):- (9,16)
$$(9-12)^2+(16-10)^2=3^2+6^2=45 < 64$$.
Hence, the point lies inside the circle.
Case (vi):- (16, 4)
$$(16-12)^2+(4-10)^2=4^2+6^2=52 < 64$$.
Hence, the point lies inside the circle.
Case (vii):- (16, 16)
$$(16-12)^2+(16-10)^2=4^2+6^2=52 < 64$$.
Hence, the point lies inside the circle.
A total of 6 perfect square points lie inside the circle.
Option 'C' is the answer.
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