Tuesday, December 4, 2012

vectors and angles




Here are some two dimensional vectors. Find the difference between the vectors, both U-V and V-U, the dot products U·U, V·V, U·V, length of the vectors and the cosine of the angle between them, which is given by the formula in the picture above.

Example

U = <4 3> and V = <0 5>

U·U =  25

V·V =  25

U·V = 15

||U|| = sqrt(25) = 5

||V|| = sqrt(25) = 5

costheta = 15/25 = 3/5

theta ~= 53.1301°

Practice.

U = <4 3> and V = <3 -4>

U·U = ______

V·V =  ______

U·V =______

||U|| = ______

||V|| = ________

costheta = ______

theta = _______

U-V = _______

||U-V|| = _________

cosine of angle between U and U-V = ________


angle to nearest thousandth of a degree = _______


V-U = _______

||V-U|| = _________

cosine of angle between V and V-U = ________


angle to nearest thousandth of a degree = _______



Answers in the comments.

1 comment:

  1. U = <4 3> and V = <3 -4>

    U·U = 25

    V·V = 25

    U·V = 0

    ||U|| = 5

    ||V|| = 5

    costheta = 0

    theta = 90°

    U-V = <1 7>

    ||U-V|| = sqrt(50) = 5sqrt(2)

    cosine of angle between U and U-V = 25/5*5*sqrt(2) = 1/sqrt(2) = sqrt(2)/2


    angle to nearest thousandth of a degree = 45° exactly


    V-U = <-1 -7>

    ||V-U|| = 5sqrt(2)

    cosine of angle between V and V-U = sqrt(2)/2


    angle to nearest thousandth of a degree = 45° exactly

    ReplyDelete