Datrys cos(5pidiv6)

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

Enrhifo

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

Camau Ateb

Defnyddio \cos(x+y)=\cos(x)\cos(y)-\sin(y)\sin(x) lle mae x=\frac{\pi }{2} a y=\frac{\pi }{3} i gael y canlyniad.

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

Cael gwerth \cos(\frac{\pi }{2}) o’r tabl gwerthoedd trigonometrig.

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

Cael gwerth \cos(\frac{\pi }{3}) o’r tabl gwerthoedd trigonometrig.

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

Cael gwerth \sin(\frac{\pi }{3}) o’r tabl gwerthoedd trigonometrig.

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

Cael gwerth \sin(\frac{\pi }{2}) o’r tabl gwerthoedd trigonometrig.

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

Gwnewch y gwaith cyfrifo.

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