Question

How do you solve this without using a calculator

Answer 1

Answer:

A

Explanation:

You must know the basics of Trigonometry to solve this.

First, you must know that

$\frac{3\pi}{4}$

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

$\cos( \frac{3\pi}{4} ) = \frac{ \sqrt{2} }{2}$

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

So the answer is A