A circle is centered at H (4,0) and has a radius of 10. Where does the point L(-2,8) lie? (khan)
a. inside the circle
b. on the circle
c. outside the circle

Respuesta :

Answer:

b) on the circle

The point lies on the circle S =0

Step-by-step explanation:

Step(i):-

Given center of the circle = H(4,0)

Radius of the circle 'r' = 10

Equation of the circle

[tex](x -h)^{2} +(y-k)^{2} = r^{2}[/tex]

[tex](x -4)^{2} +(y-0)^{2} = 10^{2}[/tex]

[tex](x )^{2} -8 x + 16 + (y)^{2} = 10^{2}[/tex]

[tex](x )^{2} -8 x + (y)^{2} = 10^{2} - 16[/tex]

[tex]x ^{2} -8 x + y^{2} = 84[/tex]

Step(ii):-

S =0 is a circle and P(x₁ , y₁) be a point in its plane

Then (i) P lies inside the circle S = 0 ⇔ S₁₁ < 0

         ii) P lies outside the circle S = 0 ⇔ S₁₁ > 0

        iii) P lies on the circle S = 0 ⇔ S₁₁ = 0

now

[tex]S_{11} = x^{2} _{1} + y^{2} _{1} + 2 g x_{1} + 2 f y_{1} +c[/tex]

[tex]S_{11} = x_{1} ^{2} -8 x_{1} + y_{1} ^{2} = 84[/tex]

Given point ( -2 , 8)

[tex]S_{11} = (-2) ^{2} -8 (-2) + (8) ^{2} -84 = 0[/tex]

P lies on the circle S = 0 ⇔ S₁₁ = 0