Answer:
c. 108.4
Explanation:
cos theta = (u dot v)/ (||u|| ||v||)
where dot stands for dot product and || || is the magnitude
u = (1,5) v= (7,-4)
u dot v = (1*7 + 5*-4) = 7-20 = -13
||u|| = sqrt( 1^2 +5^2) = sqrt(1+25) = sqrt(26)
||v|| = sqrt(7^2 + (-4)^2) = sqrt(49+16) = sqrt(65)
cos theta = -13/ sqrt(26) sqrt(65)
cos theta = -13 /sqrt(1690)
theta = arccos (-13/sqrt(1690))
theta = 108.43