Rozwiąż
: 3 cze 2007, o 14:23
Wykaż że \(\displaystyle{ cos20^{\circ}* cos40^{\circ}*cos60^{\circ}*cos80^{\circ}}\)=\(\displaystyle{ \frac{1}{16}}\)
\(\displaystyle{ cos20^{\circ}* cos40^{\circ}*cos60^{\circ}*cos80^{\circ}=\frac{2sin 40^{\circ}cos40^{\circ}*cos60^{\circ}*cos80^{\circ}}{2sin 40^{\circ}}=....}\)
\(\displaystyle{ cos60^{\circ}=\frac{1}{2}}\)