What is the equation of a circle that has radius #r# centred on the origin?

Question

How do you write the general form given a circle that passes through the given points. P(-2, 0),...
What is the equation of the circle with a center at #(7 ,1 )# and a radius of #2 #?
What is the equation of the circle with a center at #(3 ,1 )# and a radius of #2 #?
What is the equation of the circle with a center at #(3 ,1 )# and a radius of #1 #?
What is the equation of the circle with a center at #(3 ,5 )# and a radius of #1 #?
What is the equation of the circle with a center at #(3 ,5 )# and a radius of #6 #?
What is the equation of the circle with a center at #(2 ,5 )# and a radius of #6 #?
What is the equation of the circle with a center at #(2 ,2 )# and a radius of #4 #?
What is the equation of the circle with a center at #(2 ,2 )# and a radius of #3 #?
What is the equation of the circle with a center at #(2 ,1 )# and a radius of #3 #?

2185 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2017-07-06T17:11:40

# x^2 + y^2 = r^2 #

The standard equation of a circle with centre #(a,b)# and radius #r# is:

# (x-a)^2 + (y-b)^2 = r^2 #

Thus the equation we seek with centre #(a,b)=(0,0)# is:

# (x-0)^2 + (y-0)^2 = r^2 #

i.e.

# x^2 + y^2 = r^2 #