Circles Flashcards
1
Q
general formula of a circle
A
(x-x1)+(y-y1)=r²
2
Q
if the diameter AB forms a triangle ABC with C at a point on the circle then what angle is 90°?
A
angle BAC (with diameter as the hypothenuse)
3
Q
what is the relationship between a chord and a radius?
A
the radius perpendicularly bisects the chord
4
Q
how would you work out how many times a line intersects a circle?
A
solve the circle and like equation simultaneously and use the discriminant:
- b²-4ac<0, line DOES NOT intersect
- b²-4ac=0, line is a TANGENT
- b²-4ac>0, line intersects TWICE
5
Q
how would you tell if point P lies inside or outside of the circle?
A
- (CP)² < r², P is inside circle
- (CP)² = r², P is on circle
- (CP)² > r², P is outside of circle
6
Q
what is the relationship between tangents to a circle from the same point (off the circle)?
A
they are equal lengths
