Question

Find the exact value of cos(-7pi/4)

Answer 1

pi meaning 3.14...?

Answer 2

yeah

Answer 3

so that would be -7 times 3.14/4

Answer 4

okay... so first times -7 by 3.14

Answer 5

which is -21.98

Answer 6

next divid -21.98 by 4

Answer 7

which gives you -5.495

Answer 8

\(\cfrac{7}{4}\implies \cfrac{4+3}{4}\implies \cfrac{\cancel{4}}{\cancel{4}}+\cfrac{3}{4}\implies 1+\cfrac{3}{4}
\\ \quad \\
\cfrac{7\pi }{4}\implies \cfrac{4\pi +3\pi }{4}\implies \cfrac{\cancel{4}\pi }{\cancel{4}}+\cfrac{3\pi }{4}\implies \pi +\cfrac{3\pi }{4}
\\ \quad \\
-\cfrac{7\pi }{4}\implies -\cfrac{4\pi +3\pi }{4}\implies -\cfrac{\cancel{4}\pi }{\cancel{4}}-\cfrac{3\pi }{4}\implies -\pi -\cfrac{3\pi }{4}\)

Answer 9

hope that helps :)

Answer 10

bear in mind that, when using a fraction of \(\pi\), is still just a fraction, so, you can siimply take the "wholes" from it, like on any fraction

Answer 11

@Wow2007 was that correct?

Answer 12

No, because they have to be in like fraction form

Answer 13

No, because they have to be in like fraction form

Answer 14

so... what quadrant did you end up at anyway?

Answer 15

Answer A is (sqrt)2/2
Answer B is 1/2
Answer C is (sqrt)3/2
Answer D is -1/2

Answer 16

I don't know, I have literally no math skills at all, I've always been way behind in math

Answer 17

well... have you covered negative angles yet?

Answer 18

Not really, these lessons are kind of everywhere. like the test before this was about surveys :/

Answer 19

The book helps absolutely nothing, the only thing that is in it are definitions and examples

Answer 20

so... if you haven't covered negative angles... how are you expected to answer it?

I mean, I could ask you for my car keys only if I already know you know how to find them
otherwise, it would just make no sense

I mean, I could ask you just now
do you know where my car keys are?

Answer 21

*sigh* I know, and like you have free tutoring but its literally near impossible to get ahold of a tutor and then they want you to spend like a month learning about all kinds of things and only like 5% of it is relevant.

Answer 22

I only have like 5 classes left (this is my last math) and i keep getting stuck on my math classes and it takes forever

Answer 23

well, unless you cover the material first, it won't make much sense

Answer 24

http://www.mathopenref.com/trigany.html <--- drag the corner over, notice when it turns negative