Question

Cum rezolv asta: cos7π/12 ?

Answer 1

$cos( \frac{7 \pi }{12})= cos ( \frac{4 \pi }{3} + \frac{3 \pi }{3} )= cos \frac{ \pi }{3} * cos \frac{ \pi }{4} - sin \frac{ \pi }{3} * sin \frac{ \pi }{4}= \frac{1}{2} * \frac{ \sqrt{2} }{2}- \frac{ \sqrt{3} }{2} \frac{ \sqrt{2} }{2}$

= $\frac{ \sqrt{2}- \sqrt{6} }{4}$