I have a sphere at origin and a known 3d point outside the sphere.

How do I calc the diameter of the cone created by the 3d point

and it's intersection with the sphere (if that makes sense)

Thanks

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- May 21st 2006, 10:27 AMBlain[SOLVED] Finding diameter of a cone
I have a sphere at origin and a known 3d point outside the sphere.

How do I calc the diameter of the cone created by the 3d point

and it's intersection with the sphere (if that makes sense)

Thanks - May 21st 2006, 11:13 AMearbothQuote:

Originally Posted by**Blain**

I've attached a diagram to show you what I've calculated.

All lines PT form a cone. C is the centre of the sphere. All triangles CTP are right triangles. So the diametre of the cone's base is 2 times the height in the right triangle. The height in a**right triangle**(and only there) can be calculated by:

$\displaystyle h={{r \cdot TP}\over CP}$

If you know the length of the three lines you only have to plug in the values and caculate the radius of the base.

Greetings

EB - May 21st 2006, 08:45 PMearbothQuote:

Originally Posted by**Blain**

it's me again:

I've attached a picture which shows sphere and cone from outer space. May be this will help to understand my previous diagram.

Greetings

EB