equation of a circle Flashcards
1
Q
When the origin is (0,0) the radius of a circle is
A
x²+y²=r²
2
Q
when it is centre (a,b) and radius r
A
(x-a)² + (y-b)² =r²
3
Q
general eqn of a circle
A
x²+y²+2fx+2gy+c=0
4
Q
The centre of a circle (a,b) is given by
A
(-1/2 coeff. of x, -1/2 coeff. of y)
5
Q
radius of circle is given by
A
√a²+b²-c
6
Q
the grad of the normal to the circle P
A
1) determine the center
2) find gradient using the points given and center
7
Q
the grad of tangent
A
perpendicular to grad. of the normal
8
Q
In order to find the points of intersection of a circle and a straight line
A
we solve the two equations simultaneously
