9514 1404 393
Answer:
31°
Step-by-step explanation:
One way to find the difference angle is to look at the angle of the quotient. We can use complex numbers to represent the vectors for the purpose of that math. The magnitude is not important in this problem, so we do not have to finish the division.
(8 -2i)/(5 -5i) = (8 -2i)(5 +5i)/((5 -5i)(5 +5i)) = (40 -10i +40i +10)/( )
The numerator is 50 +30i, which has an angle of ...
arctan(30/50) ≈ 30.96° ≈ 31°
_____
Additional comment
Effectively, we have found the angle as the angle of the product of one vector with the conjugate of the other, when written as complex numbers. In vector terms, you might use the definition of the dot product. That seems to take a lot more math.
u·v = |u|×|v|×cos(θ)
θ = arccos(u·v/(|u|×|v|))
θ = arccos((8·5 +(-2)(-5))/√((8² +(-2)²)(5² +(-5)²))) = arccos(50/√3400)
