Given vector = \(-\hat i + \hat j\)
Magnitude will be = \(\sqrt{1 + 1}\) = \(\sqrt 2\)
Angle
\(cos \theta = \frac {i.(-\hat i + \hat j)}{|i||-i + j|}\)
\(= \frac{-1}{1 \times \sqrt 2}\)
\(cos \theta = \frac {-1}{\sqrt 2}\)
\(cos \theta = cos 135° \)
\(\theta = 135° \)