Question

Find the exact values of cos (3pi/4radians) and sin (3pi/4 Radians)

Answer 1

`\cos(3\pi)/(4)=\cos\left(\pi-(\pi)/(4)\right)=-\cos(\pi)/(4)=-(\sqrt2)/(2)`


`\sin(3\pi)/(4)=\sin\left(\pi-(\pi)/(4)\right)=\sin(\pi)/(4)=(\sqrt2)/(3)`

Look at the picture.


`(\pi)/(2) < (3\pi)/(4) < \pi\\\\therefoere\\\\\cos(3\pi)/(4) < 0\ and\ \sin(3\pi)/(4) > 0`