Datrys cos5pi/4

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

Enrhifo

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

Camau Ateb

Defnyddio \cos(x+y)=\cos(x)\cos(y)-\sin(y)\sin(x) lle mae x=\pi a y=\frac{\pi }{4} i gael y canlyniad.

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

Cael gwerth \cos(\pi ) o’r tabl gwerthoedd trigonometrig.

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

Cael gwerth \cos(\frac{\pi }{4}) o’r tabl gwerthoedd trigonometrig.

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

Cael gwerth \sin(\frac{\pi }{4}) o’r tabl gwerthoedd trigonometrig.

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

Cael gwerth \sin(\pi ) o’r tabl gwerthoedd trigonometrig.

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

Gwnewch y gwaith cyfrifo.

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