Question

Cos(-13pi/12)?

Answer 1

so you want to break this down into cos(a-b)?

Answer 2

yes

Answer 3

ok i cant work it out all the way but, here is a great start

Answer 4

\[\cos(\frac{ -7\pi }{ 6}-\frac{ 3\pi }{ 6 })\]

Answer 5

hmmm, nm thats wrong

Answer 6

cos(-3pi/12-5pi/6)

Answer 7

ok ill check

Answer 8

you know the identity?

Answer 9

cos(-pi/4-5pi/6) = cos(a-b) = cosa(cosb)+sina(sinb)

Answer 10

plug those in and solve

Answer 11

thats how its done :)

Answer 12

have to go, good luck

Answer 13

yeah i do