Answer
$1,70.5^\circ$
Work Step by Step
1. Given $\vec v=i+j+k, \vec w=i-j+k$, we have $\vec v\cdot\vec w=(1)(1)+(1)(-1)+(1)(1)=1$
2. We can get the angle between the vectors
$\theta=cos^{-1}(\frac{\vec v\cdot\vec w}{||\vec v || ||\vec w ||})=cos^{-1}(\frac{1}{\sqrt {1+1+1}\sqrt {1+1+1}})\approx70.5^\circ$
