Question

cos(╥ /4)cos(╥ /6)=?

Answer 1

\(\pi=180 \)
\(\cos\frac{\pi}{4}=cos\frac{180}{4}=cos45\)
do you know what is cos 45 ?

Answer 2

ok just remember the tables :
cos 45 = \(1\over2\)

similarly cos\((\frac{\pi}{6})\) = \(cos{\frac{180}{6}}\) = \(cos30 = \frac{\sqrt{3}}{2}\)
hence \(\frac{\sqrt{3}}{2}*\frac{1}{2}=\frac{\sqrt{3}}{4}\)