Question

Find the angle θ between u = <7, –2> and v = <–1, 2>.

Answer 1

Answer:

132.5°

Step-by-step explanation:

u•v = |u| |v| cos(theta)

(7×-1) + (-2×2) = sqrt(53) × sqrt(5) cos(theta)

-7-4 = sqrt(265) cos(theta)

cos(theta) = -11/sqrt(265)

theta = 132.510447078

Answer 2

The angle between two vectors is:

CosФ = u - v / Magnitude(u) x magnitude(v)

Magnitude of u = SQRT(7^2 + -2^2) = SQRT(49 +4) = SQRT(53)

Magnitude of v = SQRT(-1^2 +2^2) = SQRT(1 +4) = SQRT(5)

u x v = (7 x -1) + (-2 x 2) = -7 + -4 = -11

cosФ = -11 / sqrt(53) x sqrt(5)

cosФ = -11sqrt265) / 265

Ф =cos^-1(-11sqrt265) / 265)

Ф=132.51 degrees.