Question

Find the exact values of cos 3 pi/4 radians sin 3 pi/4 radians.

Answer 1

If you consult the unit circle, you will see that:


`cos((3\pi)/(4)) = -(√(2))/(2)\\\\sin((3\pi)/(4)) = (√(2))/(2)`

3pi/4 in degrees is 3pi/4 * 180/pi = 3/4 * 180 = 135 degrees. And please refer to the attachment to how you can obtain the values above.

Now, lets multiply it together.


`-(√(2))/(2) \cdot (√(2))/(2) =\\\\-(2)/(4) =\\\\ \boxed{\bf{-(1)/(2)}}`

So, cos(3pi/4)sin(3pi/4) = -1/2