Question

Find the value of $\cos (29\pi /3)?$

• A. $1$
• B. $0$
• C. $\frac{\sqrt{3}}{2}$
• D. $1/2$

Answer 1

Answer: (D)

$\cos \left(29\frac{\pi }{3}\right)=\cos \left(\frac{(27+2)\pi }{3}\right)$
$=\cos \left(9\pi +\frac{2\pi }{3}\right)$
$=-\cos \frac{2\pi }{3}=-\cos \left(\frac{\pi }{2}+\frac{\pi }{6}\right)=\sin \frac{\pi }{6}=\frac{1}{2}$