Answer:
cos (
) = 
Decimal value: −0.9238795325...
Step-by-step explanation:
Write,
cos
= cos
= −cos 
Now using half angle formula, cos(x) = 2 cos²(
) − 1, we can write cos
= 2
cos²(
) − 1
This means
+ 1 = 2 cos²(
)
2 cos²(
) = 
cos²(
) = 
cos(
) = 
Simplify,
=
= 
Hence,
cos (
) = −cos (
) = 
The answer has to be 1 because anything times 1 in this case 6 has to be its own self.
The answer is (20,0). We can determine the sum of two vector points by adding x1 to x2 and y1 to y2. This is like adding integers, the only difference is the answer is in vector form. In here, we have (x,y). x = 7+13 and y = 5+(-5). that is why we have the (20,0) as the answer.