I don’t know how Sunday afternoon goes down at your house, but here’s how it goes down at mine. I can usually be found watching some NFL game I don’t really care about while working on my laptop doing a few math and/or administrative tasks. Sitting next to me is one of my kids, or one of my kids’ friends, doing online calculus or statistics homework and occasionally asking me questions. There is probably some drumming going on in the background because, well, if you know you know. Then, PING, a message comes in from someone who is doing their version of Sunday afternoon at their house.

Any chance you know of a secret to find these 2 angles? I’m looking to cut the sides of a bookshelf so I can put the top back on and have it snug to the ceiling.

And then a picture.

And then another picture.

Ok for those of you who know how to answer the question, stop reading and start calculating. Then come back and see if you were correct. For the rest of you, keep reading.

So, I drew my own picture, which included an additional horizontal line and labeled angles, and made some calculations. 47 – 29.25 = 17.8 (ish). To find the measure of angle A, use tangent because you have the opposite (17.8) and the adjacent (31.75). Because you are looking for the angle, use inverse tangent. Make sure you are in degree mode!

A = 28.5 degrees and so B = 180 – 90 – 28.5 = 61.5 degrees. The obtuse angle needed would be A + 90 = 28.5 + 90 = 118.5 degrees.

So I sent those two important angle measures back… 118.5 degrees and 61.5 degrees. About 45 minutes later, I got pictures of the finished shelving!

Now, this person I helped thinks I am some sort of math genius, but this is a high school geometry problem! Definitely not genius level. What this person needs to realize is how amazing she is! Successful people do three things well:

1. Take the initiative to ask questions (never be shy about this).
2. Use their resources (youtube videos, friends, etc.) wisely.
3. Communicate clearly (look at the great measurements and drawing).

And alllll of us can get better at the above three things.

You might like some of my other posts about Math in Real Life…

Math in Real Life

When Are We Ever Going To Use This?

More From The “When are we ever going to use this?” File