Question

Can someone please help me

Answer 1

see explanation

Explanation:

`(3\pi )/(4)` is an angle in the second quadrant where sin > 0 and cos < 0

cos(
`(3\pi )/(4)` )

= cos (π -
`(3\pi )/(4)` )

= - cos (
`(\pi )/(4)` )

= -
`(√(2) )/(2)`

and similarly

sin (
`(3\pi )/(4)` )

= sin (
`(\pi )/(4)` )

=
`(√(2) )/(2)`