Equation of a circle

Question 1

The equation of a circle is helpful for when?

Answer 1

When they graph a circle on a coordinate plane

Question 2

What is also important to think about when you see a circle graphed in the x y coordinate plane?

Answer 2

right triangles and the Pythagorean theorem

Question 3

What is the formula for the equation of a circle graphed at the origin?

Answer 3

x^2 + y^2 = r^2

where the x and the y stand for the coordinates of a point actually on the outside of the circle

r is the radius

Question 4

What is the Pythagorean theorem ?

Answer 4

x^2 + b^2 = c^2

Question 5

When calculating if a point is inside, outside or on the circle use the x^2 + y^2 = r^2 formula.

If r you have the radius, for example r = 13, how do you know if a point is on the circle, inside or outside?

Answer 5

13^2 = 169
So, if x^2 + y^2 is greater than 169 then the point is outside the circle

if x^2 + y^2 is less than 169 then the point is inside the circle

and if x^2 + y^2 is equal to 169 then the point is on the circle