Question

use a double- angle identity to find the exact value
sin22.5^ocos22.5^o

Answer 1

why I am still at 19 fans, after spending the last 5 hours working my *** out?

Answer 2

if you help me with this i will become a fan

Answer 3

ok, one min

Answer 4

the double angle identities are as follows:

\[\cos (A - B) = (\cos A)(\cos B) + (\sin A)(\sin B) \]
\[\cos (A + B) = (\cos A)\cos B - (\sin A)\sin B \]
\[\sin (A + B) = (\sin A)(\cos B) + (\cos A)(\sin B) \]
\[\sin (A - B) = (\sin A)(\cos B) - (\cos A)(\sin B) \]

alright andy :) you can lead from here ^_^

Answer 5

hmm, am I mixing it all up with the double angle identities? those are the sin and cos indentities , hmm, please correct me if I'm wrong ^_^

Answer 6

double angle identities go like this, egzample:
sin(2x)=2sinxcosx

Answer 7

That is just the above with setting A=B

Answer 8

no the identities are
sin2A=2sineAcosA
cos2A-cos^2A-sin^2A
=1-2sin^2A
=2cosA-1

Answer 9

or right lol , thank you, alright angoo, give it a try ^_^

Answer 10

ok I am bad at this, I guess I must have skipped school the day this stuff was tought

Answer 11

give it a try :)

Answer 12

yeah same here

Answer 13

nah, stary, you go ahead, I dont get this stuff yet

Answer 14

ask your beloved google lol

Answer 15

well, Google can give me examples, and explanations, and I can learn from them, but it would take too much time... so just go ahead and do it mimi

Answer 16

this is my new signature btw:

▓▒░╔ᴧᴨᴅᴙiᴜs╖░▒▓

Answer 17

LOL

Answer 18

alright LoveL , let me get this clear :

you want to find the answer of :

sin(22.5)cos(22.5)? or do you want to find the exact angle for sin(22.5)=? or cos(22.5)=? ^_^

lol, it's filled with mystery, but I like it :)

Answer 19

I will show you, first of all: \[\sin (22.5^\circ)\cos(22.5^\circ) = \sin(\frac{180^\circ}{8})\cos(\frac{180^\circ}{8}) = \sin(\frac{π}{8})\cos(\frac π 8)\]

Answer 20

nvm, follow up with nowhereman ^_^ he'll lead you through.

Answer 21

so, loveinglife, do you feel happy today? because I do, but I could become even more happy if you gift me a fan =D

In that case, I will give you a fan too, so you become a lifesaver, and I become a superstar, a clear winwin =D

Answer 22

LOL, and you're still on it

Answer 23

@BecomeMyFan im your fan now. thank you for trying

Answer 24

Then \[\sin(\frac π 8)\cos(\frac π 8) = \frac 1 2 \cdot \left(2\sin(\frac π 8)\cos(\frac π 8)\right)\] Thus by applying that double arc formula on the inner part (in reverse direction if you want) you get \[=\frac 1 2 \sin(2\frac π 8) = \frac 1 2\sin(\frac π 4) = \frac 1 4 \sqrt 2\]

Answer 25

Oh my god your awesome. thank you soo much you just saved my trig grade

Answer 26

You're welcome :-D

Answer 27

love, are you in highschool?

Answer 28

or in college

Answer 29

?

Answer 30

because if you are doing this stuff in high school, I must have skipped ALOT of it

Answer 31

im saddly in college and i thought i was good in math till i got here

Answer 32

:)

Answer 33

why am I still a mear star?

Answer 34

I wanna be a superstar

Answer 35

it was supposed to rhyme

Answer 36

=D

Answer 37

sorry cant help you there but im done, but i will probably be back at some point

Answer 38

it is part of a poem I am writting about OpenStudy

Answer 39

=)

Answer 40

you write poems?