Question

Find the exact value by using a half-angle identity.

cos(-pi/8)

Answer 1

@misty1212

Answer 2

hi!!

Answer 3

\[-\frac{\pi}{8}\] is half of \(-\frac{\pi}{4}\) use the half angle formula with that one

Answer 4

\[\cos (-\theta) = \cos \ theta]

Answer 5

\[\cos (-\theta) = \cos \theta\]

Answer 6

\[\cos (-\frac{ \pi }{ 8 }) = \cos \frac{ \pi }{ 8 }\]

Answer 7

\[\cos(-\frac{\pi}{8})=\sqrt{\frac{1+\cos(-\frac{\pi}{4})}{2}}\]

Answer 8

or as @dayakar pointed out, you can use \[\cos(\frac{\pi}{8})=\sqrt{\frac{1+\cos(\frac{\pi}{4})}{2}}\]

Answer 9

you know \(\cos(\frac{\pi}{4})\) ?

Answer 10

rad 2/2

Answer 11

\[\cos \frac{ \pi }{ 8 } = \cos \frac{ 180 }{ 8 }\]
cos 45

Answer 12

what is cos 45 value

Answer 13

sq root 2/2

Answer 14

no check again

Answer 15

.707

Answer 16

what is that

Answer 17

?

Answer 18

\[\cos 45 =\frac{ 1 }{ \sqrt{2} }\]

Answer 19

yes you are right, it is \(\frac{\sqrt2}{2}\)

Answer 20

\[\cos(\frac{\pi}{8})=\sqrt{\frac{1+\frac{\sqrt2}{2}}{2}}\]

Answer 21

simplify the compound fraction by multiplying top and bottom by 2 inside the radical

Answer 22

sq root 2/2

Answer 23

\[1/2\sqrt{1+\sqrt{2}}\] would this be the answer?

Answer 24

@misty1212