# Thread: How to show work (Unit circle)

1. ## How to show work (Unit circle)

Find all the possible angles for A if 0 ≤ A ≤ 2 (pi)

I) cosA = -1/(square root of 2)

Alright so I know the answer is 3pi/2 and 5pi/2..

How would I show the work to solve for thsee problems though? Thanks for the help

2. Check again beacuse $\displaystyle \cos{x} = -\frac{\sqrt{2}}{2}$ at 135 and at 225 degrees

3. are you sure?? I have a test on this soon and this is from hwk throughout the course... I have a website that the teacher gave which says otherwise..

http://math.hhpnet.com/mhf4u1/downlo...ngles%20II.pdf

It's for question 2 a)...

I ahve the answers but I want to know how to solve problems like these without the answers , and mainly the steps to get the answer.

Thanks

4. Originally Posted by agent2421
are you sure?? I have a test on this soon and this is from hwk throughout the course... I have a website that the teacher gave which says otherwise..

http://math.hhpnet.com/mhf4u1/downlo...ngles%20II.pdf

It's for question 2 a)...

I ahve the answers but I want to know how to solve problems like these without the answers , and mainly the steps to get the answer.

Thanks
I could not open the link due to my secruity settings but yep I'm sure I'm right.

What you have to remember is the values for cos x

$\displaystyle \cos{0} = 1$

$\displaystyle \cos{30} = \frac{\sqrt{3}}{2}$

$\displaystyle \cos{45} = \frac{\sqrt{2}}{2}$

$\displaystyle \cos{60} = \frac{1}{2}$

$\displaystyle \cos{90} = 0$

Now use reference angles to to determine what the degree would be. It would have to be in the 2nd and 3rd quad since x is negative.