Réitigh cos(5pidiv6)

$$\cos ( 5 \pi \div 6 )$$

Luacháil

$$-\frac{\sqrt{3}}{2}\approx -0.866025404$$

Céimeanna Réitigh

Bain úsáid as \cos(x+y)=\cos(x)\cos(y)-\sin(y)\sin(x) nuair atá x=\frac{\pi }{2} agus y=\frac{\pi }{3}ann chun an toradh a fháil.

$$\cos(\frac{\pi }{2}+\frac{\pi }{3})=\cos(\frac{\pi }{2})\cos(\frac{\pi }{3})-\sin(\frac{\pi }{3})\sin(\frac{\pi }{2})$$

Faigh luach do\cos(\frac{\pi }{2})ón dtábla luachanna triantánúla.

$$0\cos(\frac{\pi }{3})-\sin(\frac{\pi }{3})\sin(\frac{\pi }{2})$$

Faigh luach do\cos(\frac{\pi }{3})ón dtábla luachanna triantánúla.

$$0\times \frac{1}{2}-\sin(\frac{\pi }{3})\sin(\frac{\pi }{2})$$

Faigh luach do\sin(\frac{\pi }{3})ón dtábla luachanna triantánúla.

$$0\times \frac{1}{2}-\frac{\sqrt{3}}{2}\sin(\frac{\pi }{2})$$

Faigh luach do\sin(\frac{\pi }{2})ón dtábla luachanna triantánúla.

$$0\times \frac{1}{2}-\frac{\sqrt{3}}{2}\times 1$$

Déan áirimh.

$$-\frac{\sqrt{3}}{2}$$