# Thread: Find the angles between the 3 cylinders

1. ## Find the angles between the 3 cylinders

I was trying to help someone with their homework today... but I'm just not quite sure how to go about. I don't have the exact question but...

the book says, 3 cylinders are standing upright, and they're bolted together, forming a triangle between the 3 cylinders. We're given each of the cylinder's radius, and then asked to find the angles of the triangle between the cylinders.

It's in the Law of Sine Law of Cosine section of the book, so I'm sure it's not too hard, but I'm not in the class, so I'm not really sure how to find the inner triangle.

2. Originally Posted by gummy_ratz
I was trying to help someone with their homework today... but I'm just not quite sure how to go about. I don't have the exact question but...

the book says, 3 cylinders are standing upright, and they're bolted together, forming a triangle between the 3 cylinders. We're given each of the cylinder's radius, and then asked to find the angles of the triangle between the cylinders.

It's in the Law of Sine Law of Cosine section of the book, so I'm sure it's not too hard, but I'm not in the class, so I'm not really sure how to find the inner triangle.
law of cosines ...

$\displaystyle \displaystyle \cos{A} = \frac{b^2+c^2-a^2}{2bc}$

$\displaystyle \displaystyle A = \arccos\left(\frac{b^2+c^2-a^2}{2bc}\right)$

in the formulae, note that side $\displaystyle a$ is opposite angle $\displaystyle A$

each side will be the sum of two radii as shown in the diagram ...

3. Ohh okay, that seems easy enough. See, I thought they meant that slanty triangle in between the 3 circles, and so I wasn't sure how we'd get the length of the sides of the triangle since its sides aren't even straight.