We are asked to find the angle between vectors u and v and
the projection where proj(v)u = (u*v/|v| ^ 2)v.
u=
<5,8> and v = <20,5>.
We will
first find the angle between vectors u and v.
The formula
is cos(theta) = (u *v)/(|u| *|v|)
=> cos (theta)
=
(5*20) + (8 * 5)/ [(sqrt 5^2 + 8 ^2) * (sqrt 20 ^ 2 + 5 ^
2)]
=> cos (theta)
=
(100 + 40)/(sqrt 25 +64) *(sqrt 400 +
25)
=> cos (theta) = (140) /(sqrt 89) *(sqrt
425)
=> cos (theta) = (140) / (sqrt
37825)
=> cos (theta) =
(140)/(194.4865)
=> The angle between
the two vectors is approximately 43.96
degrees.
To find the projection we use the
following formula which we were given:
=>
projection (v)u = (u * v/ |v| ^2) v
=> projection
(v)u =
{[(5 * 20) + (8 * 5)/[sqrt (20 ^2 + 5 ^2)] }* (20,
5)
=> projection (v)u = [(140)/(sqrt 425) ] *
(20,5)
=> projection(v)u = 6.79 * ( 20,
5)
=> projection(v)u = ( 135.8, 33.95
)
The angle between the two
vectors is approximately 43.96
degrees.
The projection(v)u =
( 135.8, 33.95 ).
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