# Math formula needed **URL:** \ **Category:** Factual Questions\ **Created:** [April 4, 2008, 8:32pm UTC](https://boards.straightdope.com/t/math-formula-needed/443980 "2008-04-04T20:32:12Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![Don\_t\_fight\_the\_hypothetical](https://avatars.discourse-cdn.com/v4/letter/d/59ef9b/32.png) [@Don\_t\_fight\_the\_hypothetical](https://boards.straightdope.com/u/Don_t_fight_the_hypothetical)\ **Post date:** [April 4, 2008, 8:32pm UTC](https://boards.straightdope.com/t/math-formula-needed/443980/1 "2008-04-04T20:32:12Z")
I’m looking for a formula (or an answer) to find [this angle](http://www.flickr.com/photos/24533375@N04/2387566079/) in degrees. Thanks ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [April 4, 2008, 8:48pm UTC](https://boards.straightdope.com/t/math-formula-needed/443980/2 "2008-04-04T20:48:04Z")
Imagine a triangle constructed by eliminating the left side. Then the angle is the arctangent(65.75/(41.5 - 29.75)). ---
**Author:** ![wolfman](https://avatars.discourse-cdn.com/v4/letter/w/a8b319/32.png) [@wolfman](https://boards.straightdope.com/u/wolfman)\ **Post date:** [April 4, 2008, 8:51pm UTC](https://boards.straightdope.com/t/math-formula-needed/443980/3 "2008-04-04T20:51:36Z")
Assuming the top two angles are right, just finish off the box. A right Triangle formed at the bottom with height 10.75, and length 65.75 would make it a rectangle. Then figure out the smallest angle (tan works)in the right triangle, and that subtracted from 90 is your angle. ---
**Author:** ![mks57](https://avatars.discourse-cdn.com/v4/letter/m/b9bd4f/32.png) [@mks57](https://boards.straightdope.com/u/mks57)\ **Post date:** [April 4, 2008, 8:58pm UTC](https://boards.straightdope.com/t/math-formula-needed/443980/4 "2008-04-04T20:58:53Z")
79.87 degrees ---
**Author:** ![Don\_t\_fight\_the\_hypothetical](https://avatars.discourse-cdn.com/v4/letter/d/59ef9b/32.png) [@Don\_t\_fight\_the\_hypothetical](https://boards.straightdope.com/u/Don_t_fight_the_hypothetical)\ **Post date:** [April 4, 2008, 9:04pm UTC](https://boards.straightdope.com/t/math-formula-needed/443980/5 "2008-04-04T21:04:01Z")
Thanks guys. ---
**Author:** ![ultrafilter](https://avatars.discourse-cdn.com/v4/letter/u/3d9bf3/32.png) [@ultrafilter](https://boards.straightdope.com/u/ultrafilter)\ **Post date:** [April 4, 2008, 9:10pm UTC](https://boards.straightdope.com/t/math-formula-needed/443980/6 "2008-04-04T21:10:55Z")
Assuming that the angles that look like right angles are right angles: Label the points of the quadrilateral are A, B, C and D, starting at the bottom left and going clockwise. Draw the line parallel to BC through A, and label its point of intersection with CD as E. The triangle ADE is a right triangle with legs of length 65.75" and 11.75". The hypotenuse is therefore roughly 66.79" long. The law of cosines says that c[sup]2[/sup] = a[sup]2[/sup] + b[sup]2[/sup] - 2ab\*cos(x), where c is the length of the side opposite the angle, a and b are the lengths of the sides adjacent to it, and x is the measure of the angle. Here c = 65.75", a = 11.75", and b = 66.79". Substituting and solving, I get that cos(x) = 0.1759, or x = 79.87" (just like **mks57** said). ---
**Author:** ![wolfman](https://avatars.discourse-cdn.com/v4/letter/w/a8b319/32.png) [@wolfman](https://boards.straightdope.com/u/wolfman)\ **Post date:** [April 4, 2008, 9:16pm UTC](https://boards.straightdope.com/t/math-formula-needed/443980/7 "2008-04-04T21:16:30Z")
[QUOTE=wolfman] Assuming the top two angles are right, just finish off the box. A right Triangle formed at the bottom with height\*\* 10.75\*\*, and length 65.75 would make it a rectangle. Then figure out the smallest angle (tan works)in the right triangle, and that subtracted from 90 is your angle. [/QUOTE] :smack: Stupid substraction: should be 11.75