# Equation of a sphere

1. Sep 2, 2009

### tnutty

1. The problem statement, all variables and given/known data
Find an equation of the sphere with center (1,-4,3); with radius 5.
What is the intersection of this sphere with the xz-plane?

3. The attempt at a solution

I am not sure what the second part of the equations is asking about, but the equation
of the sphere is (x-1)^2 + (y+4)^2 + (z-3)^2 = 5^2.

Any help on what the second part is about.

2. Sep 2, 2009

### espen180

You are asked to find the points on the xz-plane (y=0) where the sphere "cuts through" this plane.

For example, a line intersects a plane at the point where it passes through it.

3. Sep 2, 2009

### tnutty

So is it just the top left side of the sphere? How would I go about finding the answer?

4. Sep 2, 2009

### Staff: Mentor

espen180 gave you a hint by telling you the equation of the x-z plane.

5. Sep 3, 2009

### HallsofIvy

Staff Emeritus
Since, as espen180 said, the xz-plane is defined by y= 0, replace y with 0.