Coordinate Geometry Flashcards: Lines and Circles

Question 1

State the distance formula between $A(x_1,y_1)$ and $B(x_2,y_2)$.

Accepted Answer

$$AB=\sqrt{(x_2-x_1)^2+(y_2-y_1)^2}$$ where $(x_1,y_1)$ and $(x_2,y_2)$ are the coordinates of the two points.

Question 2

What is the difference between an undefined slope and a zero slope?

Accepted Answer

Zero slope means a horizontal line ($m=0$, equation $y=c$). Undefined slope means a vertical line ($x=c$), since $x_2-x_1=0$.

Question 3

State the standard equation of a circle with center $(h,k)$ and radius $r$, and how to identify $(h,k)$ and $r$.

Accepted Answer

$$(x-h)^2+(y-k)^2=r^2$$ where $(h,k)$ is the center and $r>0$ is the radius.

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