A circle has a center at 4 – 5i and a point on the circle at 19 – 13i. Which of the following points is also on the circle?
–11 –3i
–4.5 +3.5i
12 + 10i
21 + 12i

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Answer:

The correct option is  3.

Step-by-step explanation:

The center of the circle is (4-5i). A point on the circle at (19 – 13i).

Distance formula between two points [tex]z_1=x_1+iy_1\text{ and } z_2=x_2+iy_2[/tex] is

[tex]d=\sqrt{(x_2-x_1)^2+(y_2-y_1)^2}[/tex]

The radius of the circle is

[tex]d=\sqrt{(19-4)^2+(-13-(-5))^2}=17[/tex]

The radius of the circle is 17 units.

The distance between –11 –3i and (4-5i).

[tex]d=\sqrt{(-11-4)^2+(-4-(-5))^2}=\sqrt{226}[/tex]

The distance between –4.5+3.5i and (4-5i).

[tex]d=\sqrt{(-4.5-4)^2+(3.5-(-5))^2}=12.02[/tex]

The distance between -12+10i and (4-5i).

[tex]d=\sqrt{(12-4)^2+(10-(-5))^2}=17[/tex]

The distance between -12+10i and (4-5i) is equal to the radius. Therefore point 12+10i lies on the circle.

The distance between 21+12i and (4-5i).

[tex]d=\sqrt{(21-4)^2+(12-(-5))^2}=21.93[/tex]

Therefore option 3 is correct.