Question

Can someone PLEASE explain cos and sin?!

Answer 1

Using sine and cosine, it's possible to describe any (x,y) point as an alternative, (r,θ) point, where r is the length of a segment from (0,0) to the point and θ is the angle between that segment and the x-axis. This is called the polar coordinate system, and the conversion rule is (x,y) = (rcos(θ),rsin(θ )). 

Answer 2

Yes.

If you have a RIGHT triangle with a 29-degree angle in it, and you
divide the length of the leg adjacent to the angle by the length of the
hypotenuse, then it doesn't matter whether the triangle is drawn on
the head of a pin or on a piece of paper that reaches from the Earth
to the Moon, the quotient of (adjacent)/(hypotenuse) will always be
the same number ... about 0.875 .

That number is a property of every 29-degree angle, no matter the size
of the right triangle that it's in.  It's called the cosine of 29 degrees.

If you were to divide the leg opposite the 29-degree angle (instead of
the adjacent leg) by the length of the hypotenuse, you'd get a different
number ... about 0.485 .  That number is also a property of every 29-degree
angle, no matter the size of the triangle around it.  That one is called
the sine of 29 degrees.

I just used 29 degrees as an example.  Every angle has a sine and
a cosine, and a few other things too. 

If you have an angle, there's no easy way to calculate its sine or its
cosine.  You just have to look them up.  They're in tables in books,
or on line (just put 'cosine 29' in Google), and if you have a calculator,
they're probably on your calculator too.

You don't know yet what these are good for, or what you can do with
them.  That'll be coming up in math before you know it !

So the easiest answer to your question is:

Every angle has properties, characteristics, and aspects of its
personality that you never notice until you really get to know it. 
They're called the sine, the cosine, the tangent, the cotangent,
the secant, and the cosecant.  They're all numbers, and every
angle has a full set of them !