cos(2a+b)=4/5cos(a+b)=2/3cos(a)=? can somebody help me

[autumn anchor]

cos(2a+b)=4/5 cos(a+b)=2/3 cos(a)=?

[crimson atlas]

$cos(2a+b)=\frac{4}{5}$
\

$cos(a+b)=\frac{2}{3}$
\

Find $cos(a)$

[autumn anchor]

what is happening

[rigid lark]

FirstNameLastName

[crimson atlas]

You broke the server

[autumn anchor]

haha

bot is glicthing

fr

[crimson atlas]

I was editing it

And the bot updated the picture

[autumn anchor]

did you solved the problem ?

[crimson atlas]

Nah but I made it easier to read

I’m not familiar with the cosine rules

But I’ll give it a try anyway

[autumn anchor]

by the way i cant open a help channel

there is no channel under the how-to-get-help

[crimson atlas]

True

$cos\left(a-cos^{-1}\left(\frac{2}{3}\right)\right)=\frac{4}{5}$

[rigid lark]

FirstNameLastName

[crimson atlas]

$a=cos^{-1}\left(\frac{2}{3}\right)+cos^{-1}\left(\frac{4}{5}\right)$

[autumn anchor]

this problem has no value

[crimson atlas]

What do you mean?

[rigid lark]

FirstNameLastName

[crimson atlas]

$cos\left(a\right)=cos\left(cos^{-1}\left(\frac{2}{3}\right)+cos^{-1}\left(\frac{4}{5}\right)\right)$

[rigid lark]

FirstNameLastName

[autumn anchor]

oh sorry i found the answer key

8+3√5/15

answer

[crimson atlas]

Isn’t it $\frac{8-3\sqrt{5}}{15}$?

[rigid lark]

FirstNameLastName

[autumn anchor]

no 8+3

[crimson atlas]

Hmm

Yeah I see my mistake

@autumn anchor type .close if you need no more help

[autumn anchor]

im looking for the transactional solution

So what did we do to get this?

.close