Calling AT Math Geeks

[Tobolo]

I need to build a small house for one of our animals and I really really really suck at angles.
The problem is that I don't know how long to make the slats in the roof.

Here is what I do know:

The top angle of the triangle is going to be 100* (*= degrees)
Each side angle is going to be 40*.
The bottom line in the triangle is 20" long.

So, what are the lengths of the two side (should be the same)?

Also if anyone could tell me how to do this in the future that would be super. I appreciate it you guys!

~Tob

 

[MegaVovaN]

Really easy problem, you find this using the trig functions. Cos, Sin, or Tan, I don't remember - let me look it up...

edit: trig functions may only work with right angles x_X

edit2: If I divide this in half, I get 2 right angles! yay! let me do the math

 

[Tobolo]

LOL I looked it up and I got a little lost. I had geo 8 years ago. Then again, math was never my strong subject.

 

[BradT]

~13.05 inches

 

[RedArmy]

BradT has it right. You do it by using the law of sines. Sin 100/20=Sin 40/x

Solve for X...which as BradT said is ~13 inches.

 

[Kelemvor]

13.05"

http://www.1728.com/trig4.htm

 

[MegaVovaN]

Yeah, I did my math and it is 13.05 units.
edit: here's a PICTURE of my calculations (I did it with COS):
Triangle

 

[chuckywang]

10/cos(40)

 

[BradT]

SOH-CAH-TOA. Law of Sines as was first said by Red Army, or simply divide the triangle in half to get 90* angles.

 

[Tobolo]

thanks guys. I greatly appreciate it. Hopefully I can pull this off next time on my own :-D

 

[dighn]

see, math is useful in everyday life after all!

 

[MegaVovaN]

Originally posted by: Tobolo
thanks guys. I greatly appreciate it. Hopefully I can pull this off next time on my own :-D

Check my 1337 illustration, and you will understand. It's simple
Triangle

 

[CraKaJaX]

Originally posted by: dighn
see, math is useful in everyday life after all!

Geometry - possibly.
Derivatives? - no.

 

[DrPizza]

Actually, wouldn't you want the roof to hang over about 2 to 3 inches to keep water from potentially seeping in where the roof meets the wall?