Issolvi cos5pi/4

$$\cos \frac { 5 \pi } { 4 }$$

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=\pi u y=\frac{\pi }{4} biex tikseb ir-riżultat.

$$\cos(\pi +\frac{\pi }{4})=\cos(\pi )\cos(\frac{\pi }{4})-\sin(\frac{\pi }{4})\sin(\pi )$$

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

$$-\cos(\frac{\pi }{4})-\sin(\frac{\pi }{4})\sin(\pi )$$

Ikseb il-valur ta’ \cos(\frac{\pi }{4}) mit-tabella tal-valuri trigonometriċi.

$$-\frac{\sqrt{2}}{2}-\sin(\frac{\pi }{4})\sin(\pi )$$

Ikseb il-valur ta’ \sin(\frac{\pi }{4}) mit-tabella tal-valuri trigonometriċi.

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

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

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

Agħmel il-kalkoli.

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