How does a compare to b a=cos(0+2pi) b=cos(-0)

You can use the double angle formula for A.
Cos(0 + 2pi) = Cos(0)*Cos(2*pi) - Sin(0)*Cos(2*pi)
Cos 0 = 1
Cos (2*pi) = 1
Sin(0) = 0
So you are left with cos(0 + 2pi) = 1 * 1 = 1

there are a couple of ways of handling Cos(-0) 
The First and most obvious way is to put it in your calculator just as you see it. Most calculators would do it like this
Cos(
+/-
0
)
=
The result should be 1
You could try using cos(0-0) You will get the same answer -- 1.

He is right i did this thing before

One shot. if 60% of 10 is 6, then what is 70%? we know it would be seven (since 60% is mathematically 60/100, or 6/10, then 70% is 70/100, or 7/10) but we can check anyway using ratios: 6 : 60% = x : 70%*inverse multiplicationx * 60% = 6 * 70%*divide both sides by 60%x = (6 * 70%) / 60%x = 7and since he has made 6 shots already, he would need just one more to get 7 shots or 70%. if the explanation is too confusing, comment and i will try to