Question

How do you solve this without using a calculator

Answer 1

A

Step-by-step explanation:

You must know the basics of Trigonometry to solve this.

First, you must know that

`(3\pi)/(4)`

lies in the second quadrant, so sin is negative.

Next, since

pi/4, is the reference angle of 3 pi/4, this means that we can set up a right triangle with pi/4 as an angle, we get

`\cos( (3\pi)/(4) ) = ( √(2) )/(2)`

`\sin( (\pi)/(4) ) = - ( √(2) )/(2)`

So the answer is A