A diameter of a particular circle has endpoints at A(-1, -2) and B(3,10). Which of the following is the
slope of the tangent drawn to this circle at point B?

A) -1/2
B) 4/5
C) -1/3
D) -4

Respuesta :

Answer:

Option C) is correct

Step-by-step explanation:

Given: Endpoints of the diameter of the circle are A(-1, -2) and B(3,10)

To find: slope of the tangent drawn to the circle at point B

Solution:

Let [tex](x_1,y_1)=(-1,-2)\,,\,(x_2,y_2)=(3,10)[/tex]

Centre of the circle = [tex](\frac{x_1+x_2}{2},\frac{y_1+y_2}{2})=(\frac{-1+3}{2},\frac{-2+10}{2})=(1,4)[/tex]

Let [tex](h,k)=(1,4)[/tex]

Distance formula states that distance between points (a,b) and (c,d) is given by [tex]\sqrt{(c-a)^2+(d-b)^2}[/tex]

Radius of the circle = Distance between points [tex](-1,-2)[/tex] and [tex](1,4)[/tex] = [tex]\sqrt{(1+1)^2+(4+2)^2}=\sqrt{4+36}=\sqrt{40}[/tex] units

Let r = [tex]\sqrt{40}[/tex] units

Equation of a circle is given by [tex](x-h)^2+(y-k)^2=r^2[/tex]

[tex](x-1)^2+(y-4)^2=\left ( \sqrt{40} \right )^2\\(x-1)^2+(y-4)^2=40[/tex]

Differentiate with respect to x

[tex]2(x-1)+2(y-4)\frac{\mathrm{d} y}{\mathrm{d} x}=0\\\frac{\mathrm{d} y}{\mathrm{d} x}=\frac{1-x}{y-4}[/tex]

Put [tex](x,y)=(3,10)[/tex]

[tex]\frac{\mathrm{d} y}{\mathrm{d} x}=\frac{1-3}{10-4}=\frac{-2}{6}=\frac{-1}{3}[/tex]

So,

slope of the tangent drawn to this circle at point B = [tex]\frac{-1}{3}[/tex]