Question

Evaluate cos(5pi/12)

Answer 1

Use the Cos addition formula
cos(5pi/12)
cos((5*180)\12)
Cos(75)
cos(30+45)
cos30*cos45-sin30*sin45

Answer 2

Completing the multiplication will get you your answer
Let me know if you need further help

Answer 3

So it's sqrt6/4-sqrt2/4??

Answer 4

yes indeed it is

Answer 5

Thank you!!

Answer 6

How do I evaluate cos285 degrees?

Answer 7

Use the same formula and idea
Cos(360-75)
Cos(a)*cos(b)+sin(a)*sin(b)
remember that we found cos75 in the problem before
Hint, you don't need sin 75

Answer 8

I'm a bit confused. So I will put cos 360 or will split it up between the cos and I don't put sin 75?