Melody

I do not understand this question Will. Is some of the explanation missing?

Well it is a vector, more than that I do not know.

Some of the others here might be able to help you. 

Heureka and Alan are probably your best bets.

it could also be a vector.

It depends on the context.

It is 1 C 1

It means how many ways can you choose one thing from one.

The answer is 1.

I don't know either.  Not offhand anyway.

You have made a really good start. You have convince me as well as yourself :))

You should be a member. You are making a really good impression here :)

Why don't you draw it with a pair of compass on a bit of paper and then you will see.

If you do not have compasses you could use a computer program or a lid to draw the cirles.

The diameter of the lid will be the lenth of the side of the square.

Oh, i just realised that it does not have to be a square.

That will make you think harder .....

Has this or something very similar been answered about 5 times already??

It is always the acute angle from the x axis that counts.

so you either use 180 or 360

1. sin 390 

one complete revolution and 30 degrees more. That is just   sin 30

2. sec(-1290)

1390/360 = 139/36 = 3 clockwise revolutions -210

-210 is equivalent to  360-210 = 150 which is in the second quad

180-150=30

sec = 1/cos and cos is negative in the second quad so so is sec

sec(-1290)= - sec(30)

Quality street, you would have been better off to explain the process and leave some of the ordering to the asker. 

Then maybe they might have learned something.

Yes of course, I missed that one. Thanks Heureka :))