Issolvi cos(225^circ)=

$$\cos ( 225 ^ { \circ } ) =$$

Evalwa

$$-\frac{\sqrt{2}}{2}\approx -0.707106781$$

Passi tas-Soluzzjonijiet

Uża \cos(x+y)=\cos(x)\cos(y)-\sin(y)\sin(x) fejn x=180 u y=45 biex tikseb ir-riżultat.

$$\cos(180+45)=\cos(180)\cos(45)-\sin(45)\sin(180)$$

Ikseb il-valur ta’ \cos(180) mit-tabella tal-valuri trigonometriċi.

$$-\cos(45)-\sin(45)\sin(180)$$

Ikseb il-valur ta’ \cos(45) mit-tabella tal-valuri trigonometriċi.

$$-\frac{\sqrt{2}}{2}-\sin(45)\sin(180)$$

Ikseb il-valur ta’ \sin(45) mit-tabella tal-valuri trigonometriċi.

$$-\frac{\sqrt{2}}{2}-\frac{\sqrt{2}}{2}\sin(180)$$

Ikseb il-valur ta’ \sin(180) mit-tabella tal-valuri trigonometriċi.

$$-\frac{\sqrt{2}}{2}-\frac{\sqrt{2}}{2}\times 0$$

Agħmel il-kalkoli.

$$-\frac{\sqrt{2}}{2}$$