Question

Find the angle between the given vectors to the nearest tenth of a degree.
u = <8, 4>, v = <9, -9>

Answer 1

cos x = u . v / |u| |v|

where u.v is the dot product and |u| and |v| are their magnitudes

Answer 2

So cosx = (8)(9) + (4)(-9) / (1)(15) =
72 + 36 = 108 / 15 = 7.2
Right @cwrw238 ?

Answer 3

dot product is 72 - 36 = 36

Answer 4

magnitudes are sqrt(8^2 + 4^2)
and
sqrt (9^2 + (-9)^2)

Answer 5

36 / sqrt(64+16) * sqrt(81 + 81)
36/ 4sqrt5*9sqrt2

Answer 6

right

Answer 7

idk what to do next man :l

Answer 8

i get that = 0.3162
cos x = 0.3162

Answer 9

just enter this value into your calculator and press cos-1 key to get x

x is the required angle

Answer 10

Got my answer! thanks cwrw

Answer 11

yw