And My Kids Say Geometry is Worthless...

[Mark Blatter]

So I am working on building a book display that sits on a table. I think my angles are correct, but would appreciate someone else's confirmation.

Also, I am struggling to determine what X is, which is the back side of the display. I am using half inch material.

Thanks in advance.

324591

[John Gornall]

9 5/8 inches

[Lee Schierer]

X= 9-5/8, I drew it on CAD.

[mreza Salav]

X= 9.5938 which is (approximately) 9 19/32
straight forward calculation based on sin/cos

[Mark Blatter]

You guys are great. Thanks for the help.

[Charlie Velasquez]

X= 9.5938 which is (approximately) 9 19/32
straight forward calculation based on sin/cos
What calculations? To me it is not drawn to scale.

[Dave Richards]

I got about 9-19/32, too, when I drew it in SketchUp

[Dan Hintz]

What calculations? To me it is not drawn to scale.

You do it via calculation precisely because it doesn't have to be drawn to scale for the correct answer.

[Pat Barry]

Having that dimension is interesting but really isn't going to help all that much to make this project IMO. You reallly should draw it up to include the width of the boards and the joinery so you can decide how best to build it and then cut to size. At the end of the day the actual dimension isn't going to be as important as does the project look good, is it assembled well, etc.

[Clint Baxter]

If your two sides are parallel with other, (ones with the threes), your angles are not correct. Sum of your angles would equal 180. You show a 45 on the left, and a 75 at the top. This would leave you with a 60 on the right, not a 30.

Clint


So I am working on building a book display that sits on a table. I think my angles are correct, but would appreciate someone else's confirmation.

Also, I am struggling to determine what X is, which is the back side of the display. I am using half inch material.

Thanks in advance.

324591

[peter gagliardi]

If your two sides are parallel with other, (ones with the threes), your angles are not correct. Sum of your angles would equal 180. You show a 45 on the left, and a 75 at the top. This would leave you with a 60 on the right, not a 30.

Clint
That was the first thing I did , was to add up degrees- the numbers intuitively didn't make sense.

[Bill Orbine]

If your two sides are parallel with other, (ones with the threes), your angles are not correct. Sum of your angles would equal 180. You show a 45 on the left, and a 75 at the top. This would leave you with a 60 on the right, not a 30.

Clint

But it does add up! The 30 degree marked is on top side of the hypotenuse (outside the triangle in reference to the dotted line). So, if you cast an imaginary line at right angle from the point of marked 30 degree intersect to the left, the angle would be 60 degrees between the X hypotenuse and the imaginary line.

[mreza Salav]

Angles are ok, if the two left/right sides are parallel imagine a line perpendicular to two at the two left/right corners, angles of the triangle are 45, 75, 60.

As for calculations, you definitely don't need scale to do it and you also don't need the two lines with length 3.
Imagine the above line connecting the two left/right point and add another line from the peak point perpendicular to this line.
The length of this new line is sin(45)*11 3/4 = 8.3085. Once you get that distance then X = 8.3085 / sin(60).