150° € (90°;180°) => cos150°<0
Se aplica formula de reducere de la cadranul al ll -lea la cadranul l => cos150°=-cos(180°-150°)=-cos30°=
[tex] - \frac{ \sqrt{3} }{2} [/tex]
210° € (180°;270°) => sin210°<0
Se aplica formula de reducere de la cadranul al lll -lea la cadranul l => sin210°=-sin(210°-180°)=-sin30°=-1/2
m=cos150°-2sin210°=
[tex] - \frac{ \sqrt{3} }{2} - 2 \times ( - \frac{1}{2} ) = - \frac{ \sqrt{3} }{2} + \frac{2}{2} = \frac{ - \sqrt{3} + 2 }{2} [/tex]
