Find the angle between vector A and B, answer in unit of degrees?

The vectors are A=-3i+3j and B=5i+2j. Crossed together the equal 21 so I used ABsin(theta)=AxB. But I don’t get the right answer from what my homework is telling me? And help would be appreciated and quick its due in the morning!! Thanks in Advance!

Geoff:

The question you should be asking yourself is: Why do I give a shit? Unless you plan on being a math teacher when you grow up (NOT a life goal I hear often), the first time you have to deal with this type of stuff is the last time you have to deal with this type of stuff. Trust me, I’ve been out of school for twelve years and the most math I’ve had to use is figuring out how much change to give someone when they hand me 20.15 to pay for something that cost 1.85.

It’s harder than it sounds.

Anyway, you’re missing the real point here. Math teachers are notoriously unorganized. This is weird because math is a very organized subject. I remember my algebra teacher in high school shuffling in 6 minutes late with breakfast on his shirt and a trail of papers falling out of his bag behind him. The fact of the matter is that if teachers were more responsible for their things, like this lost angle, you wouldn’t have to go and find them all the time.

On the other side, however, he clearly misses his angle and wants it back. I can only assume that in his own math-nerd way this angle is like a little puppy and he’s just not complete without it. Therefore, since you clearly can’t find it on your own, and you need a good grade, here’s my advice to you:

Make a “Lost-Reward” poster, make a cute little drawing of an angle between vectors A and B, and put them up all over town. Hopefully someone has seen it and will bring it home. Angles can be tricky things to find since they like to hang out in corners and under eaves so make sure the reward you’re offering is worth the effort someone will have to put out. Another thing to watch out for are angles that look like your teacher’s angle, but aren’t the same. There are a lot of fakers out there.

Good luck, and may the force be with you.

Chris:
While the above answer is valid, I think it missed the obvious fact that this was a trick question. Really, when you get down to it, math is the universal language that binds everything together. It is the thread that runs through everything around us.

Obviously, the answer your teacher is really looking for is what are the common interests that binds vector A (you) and vector B (me). Actually, A and B are totally irrelevant here. It could just as well be the common angle between ostrich and locomotive…because of that whole universal language and we are all connected thingie I was just talking about.

The answer is really quite simple. Grilled Cheese Sandwiches. All things relate to grilled cheese sandwiches and the best ones have been heated to an internal temperature of 51 degrees Celsius. Ask anyone if they like grilled cheese and they will say “yes”. They will probably also go on to ask you if you happen to have a grilled cheese sandwich on you and if you could give it to them.

Not just people either. Animals. Plants. Inanimate objects (sometimes I stick grilled cheese sandwiches in the gas tank of my car and it is so happy that it refuses to move for a week afterwards). You know…grilled cheese sandwiches are so well loved, that perhaps THEY are the universal language. Grilled Cheese Sandwiches ARE math.

In that case…this question is not a trick question after all. ‘Vector A’ is one piece of bread. ‘Vector B’ is the other piece of bread. Therefore…the angle between them must be ‘cheese’.

Glad to help out. Don’t forget to show your work.

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