silemus.

29Angle between two vectors

Find the angle in degrees between u=(1,0)\displaystyle u = (1, 0) and v=(1,1)\displaystyle v = (1, 1).

Use cosθ = (u·v)/(|u||v|). Here u·v = 1, |u| = 1, |v| = √2, so cosθ = 1/√2, giving θ = 45°. Check: cos(45°) = 1/√2 ✓.

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