how do I determine degree of angle?

[samger2 10+ year member]

Ok...I'm on a new idea now...I want to build a box that sits flush against the back portion of my rear seat in my Cherokee and fires toward the rear of the jeep...the back seat is angled...but I don't have any tools to determine the degree of angle. Is there anyway I can do this without buying a tool?

Click to read more...

 

[mokedaddy 5,000+ posts]

Use math.

 

[samger2 10+ year member]

Fair enough. Can you help me to do so? Not sure what the formula is.

 

[Blazin_Jason 10+ year member]

Time to bust out the trig. I had to review how to do it, since I've been out of school for so long. Basically take a square and use that to figure out the height to where it is at the back of the seat top. Then measure the distance from that "plum" line to the back of the seat bottom. That should give you a triangle with the height and base. Then you can figure out the hypotenuse easily and go from there.

 

[mlstrass 5,000+ posts]

wedge2 style enclosure. Obviously the angled face will go against the rear seat...

http://www.the12volt.com/caraudio/boxcalcs.asp#wed2

 

[samger2 10+ year member]

Ok...my brain is mush.

This box isn't the box I'm using, but has the exact degree of angle that I need. I own this box and it fits perfectly in the angled area I'm dealing with.

 

[skateboardkid 10+ year member]

http://www.ajdesigner.com/phptriangle/right_triangle_pythagorean_theorem_c.php

look like its almost exactly 15 inches long, working on the angle

http://www.csgnetwork.com/righttricalc.html

68 degrees on bottom angle sloping upward

and 21 degrees from top sloping downward

other angle is 90 degrees

these are aproxamations im off by a degree or two..

also you have to subtract the 9 from 14.5 to get the 5.5" that is the length of the bottom triangle to use for calculations

 

[samger2 10+ year member]

Actually...I did a google image search for "protractor" then clicked on a pic and held the box up to the picture.

It's a 70 degree angle

 

[silvercookie 5,000+ posts]

why dont you just get a protractor?

 

[samger2 10+ year member]

Because it's 9:30pm and I don't feel like leaving the house and I'm trying to do some calculations at my computer before I start building soon.

But I'm sure I'll spend the $1 it takes to get a protractor before I actually start my project.

 

[KoalaZ 10+ year member]

Angle A: ~69.25

Angle B: ~20.75

And assuming the box you showed us, side C is about 15.5" long.

 

[maldecido33 10+ year member]

Ok...my brain is mush.
This box isn't the box I'm using, but has the exact degree of angle that I need. I own this box and it fits perfectly in the angled area I'm dealing with.

SohCahToa; Sine(theta)=opposite/hypotenuse, Cosine(theta)=adjacent/hypotenuse, Tangent(theta)=opposite/adjacent.

To find that angle, you divide the height of the triangle (14"), which is our OPPOSITE side from the bottom angle we are measuring, by the distance the slant face covers (it would be your bottom depth minus the top depth, or 5"), which is our ADJACENT side. This quotient is 2.54... . The inverse tangent of this is 1.19 radians, or 68.55 degrees.

Tangent(theta)=14/5.5

arctan(14/5.5)=68.55 degrees

edit: top angle:

tangent(theta)=5.5/14

arctan(5.5/14)=21.45 degrees

the other angle is obviously 90 degrees, and 90 + 21.5 + 68.5 = 180 degrees