Question

If $A=B+C$ have scalar magnitudes of $5,4,3$ units respectively, then the angle between $A$ and $C$ is

• A. ${\cos }^{-1}\left(\frac{3}{5}\right)$
• B. ${\cos }^{-1}\left(\frac{4}{5}\right)$
• C. $\frac{\pi }{2}$
• D. ${\sin }^{-1}\left(\frac{3}{4}\right)$

Answer 1

Answer: (A)

Here, triangle is

$\theta ={\cos }^{-1}\left(\frac{|C|}{|A|}\right)$
$\theta ={\cos }^{-1}\left(\frac{3}{5}\right)$