A community for students.
Here's the question you clicked on:
 0 viewing
anonymous
 one year ago
Find an exact value.
cos 165°
quantity square root of six minus square root of two divided by four.
quantity square root of two minus square root of six divided by four.
quantity square root of two plus square root of six divided by four.
quantity negative square root of six minus square root of two divided by four.
anonymous
 one year ago
Find an exact value. cos 165° quantity square root of six minus square root of two divided by four. quantity square root of two minus square root of six divided by four. quantity square root of two plus square root of six divided by four. quantity negative square root of six minus square root of two divided by four.

This Question is Closed

ParthKohli
 one year ago
Best ResponseYou've already chosen the best response.0\[\cos 165^{\circ} = \cos (180^{\circ}  165^{\circ})=\cos(15^{\circ})\]\[=  \cos(45^{\circ}  30^{\circ})\]

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0I thought you would do cos(165)=cos(120+45) for that part?

ParthKohli
 one year ago
Best ResponseYou've already chosen the best response.0Anything that works...

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0Okay can you help me do the problem that way?

ParthKohli
 one year ago
Best ResponseYou've already chosen the best response.0\[\cos(120 + 45) = \cos 120 \cos 45  \sin 120 \sin 45\]Do you know the values of the four trigratios?

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0Would I use the unit circle for that?

phi
 one year ago
Best ResponseYou've already chosen the best response.0yes, you can use the unit circle (at least to figure out the correct sign) for example, cos 120 on the unit circle we have dw:1438101174265:dw

phi
 one year ago
Best ResponseYou've already chosen the best response.0to find the cos 120, we first find the "principal angle" which is always the smallest angle measured from the xaxis. In this case it is the marked angle in the figure, and it is 180120= 60 degrees thus we want to find the cos 60. This is one that should be memorized. cos 60= 1/2 Next, we need to figure out the sign. As shown in the figure, the "x value" is negative we know cos = x/r (r is 1 for the unit circle), so if x is negative, then the cosine value will be negative. All of that means cos 120 =  1/2
Ask your own question
Sign UpFind more explanations on OpenStudy
Your question is ready. Sign up for free to start getting answers.
spraguer
(Moderator)
5
→ View Detailed Profile
is replying to Can someone tell me what button the professor is hitting...
23
 Teamwork 19 Teammate
 Problem Solving 19 Hero
 Engagement 19 Mad Hatter
 You have blocked this person.
 ✔ You're a fan Checking fan status...
Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.