Solution

 

a)

$$\begin{align*} A - B + C &= (-2,5, 1) - (1, 0, 3) + (4, -6, 10)\\ &\boxed{A - B + C = (1, -1, 8)} \end{align*}$$​

cosθAB​cosθAB​cosθAB​cosθAB​θAB​​=30​⋅10​(−2,5,1)⋅(1,0,3)​=300​(−2)⋅1+5⋅0+1⋅3​=300​1​=0.0577=cos−10.0577θAB​=86.69∘​​

Answer

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