Question

If \[ \vec a=i+2j-2k,\quad \vec b=6i-3j+2k, \] and \(\vec c\perp \vec a\), \(\vec c\times \vec b=i-2j-6k\), then angle between \(\vec b\) and \(\vec c\) is

• A. \(\frac{\pi}{3}\)
• B. \(\cos^{-1}\frac{29}{21\sqrt2}\)
• C. \(\frac{\pi}{4}\)
• D. \(\cos^{-1}\frac{23}{21\sqrt2}\) \bigskip

Hint:

When cross product is given, always convert into \( |\vec a||\vec b|\sin\theta \).

Answer 1

The Correct Option is D