Monday

November 24, 2014

November 24, 2014

Posted by **Knights** on Sunday, March 10, 2013 at 8:32am.

I tried using distance formula but it doesnt work? Help please thanks.

- Graphing Circles - Finding the radius -
**Reiny**, Sunday, March 10, 2013 at 9:33amsince the line y = 2 is tangent to the circle, its centre must lie on the y-axis

let the centre be (0,b)

the equation of the circle is

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

but (0,2) lies on it ----> (2-b)^2 = r^2

but (8,0) lies on it ----> 64 + (0-b)^2 = r^2

64 +b^2= r^2

then 64 + b^2 = (2-b)^2

64 + b^2 = 4-2b+b^2

60 = -2b

b = -30

the centre is (0, -30) ---> radius = 2-(-30) = 32

OR

distance from (0,b) to (0,2) must equal the distance from (0,2) to (8,0)

2-b = √(64 + b^2)

square both sides

4-2b+b^2 = 64+b^2

-2b = 60

b = -30

the radius is 2 - (-30) = 32

**Answer this Question**

**Related Questions**

GEOMETRY CIRCLES PLEASE - 1.An isosceles triangle with each leg measuring 13 cm ...

maths - there are two circles touching each other at one point. The radius of ...

Math - Circle C has radius 4 inches. Circle D had radius 9 inches. These two ...

GEOMETRY CIRCLE - 1.An isosceles triangle with each leg measuring 13 cm is ...

GEOMETRY CIRCLES PLEASE - HELP ME PLEASE. 1.An isosceles triangle with each leg...

maths - 1) Circle centre (7,-2) passes through (-2,10). Calculate radius and ...

Geomatric series - A fractal is created: A circle is drawn with radius 8 cm. ...

Please help with circle tangents geometry - Two circles of different sizes are ...

geometry - In a circle with centre P,a chord AB is parallel to a tangent & ...

GEOMETRY CIRCLES - 1. Ab is a chord of a circle with center o and radius 52 cm...