Help with angles in a roof truss

[JF.]

Hello!

I wonder if anyone here can help me calculate the miter angles a and b in the picture.
The span is 274.5cm and the pitch should be 19 degrees. The truss will be built in 45x120.

Thanks in advance!

 

[Testarn]

Since you have an assumed 90-degree angle at the center of the truss, the upper angle becomes 180-90-19=71 degrees. (180 is the sum of angles in a triangle and 90 degrees is a right angle, 19 degrees is your roof pitch) So A= 71 and B=19

 

[JF.]

Since you have a supposed 90-degree angle at the middle of the truss, the upper angle becomes 180-90-19=71 degrees.
(180 is the sum of angles in a triangle and 90 degrees is a right angle, 19 degrees is your roof pitch)
So A= 71 and B=19

Thanks for the help 👍🏻

 

[Joak]

Since you have an assumed 90-degree angle at the middle of the truss, the top angle becomes 180-90-19=71 degrees.
(180 is the sum of angles in a triangle, and 90 degrees is a right angle, 19 degrees is your roof pitch)
So A= 71 and B=19

Isn't it the opposite?

 

[Plupp 405730]

Since you have a supposed 90-degree angle at the middle of the roof truss, the upper angle becomes 180-90-19=71 degrees.
(180 is the sum of angles in a triangle and 90 degrees is a right angle, 19 degrees is your roof slope)
So A= 71 and B=19

If you're going to cut A on a miter saw, the angle is 19 degrees so I don't quite understand how you think?

 

[Testarn]

If you are going to cut A on a miter saw, the angle is 19 degrees, so I don't quite understand what you mean?

It kind of depends on what you're starting from...

If it's from the miter saw's perpendicular, i.e., 90 degrees, then you have to remove 19 degrees. That's correct.
But the triangle's angle is 71 degrees.

I think that becomes quite obvious when you're standing at your miter saw.

However, if you want to set the angle on a sliding bevel (with some form of protractor/angle gauge) and then cut with a circular saw or handsaw, it's 71 degrees that you need. On the other hand, you can cut from the "other side," and then you have to use 109 degrees....