apple_pi
Simplify
sin^2(54)+cos^2(72)



This Question is Closed

apple_pi
Best Response
You've already chosen the best response.
0
Please don't just go sin 54 = blah and cos(72) = blah, so blah + blah = blahblah

apple_pi
Best Response
You've already chosen the best response.
0
@Callisto

tukajo
Best Response
You've already chosen the best response.
0
is 54 the actual number or is that in 54 degrees?

apple_pi
Best Response
You've already chosen the best response.
0
54 degrees

zzr0ck3r
Best Response
You've already chosen the best response.
0
So you just want to know how to computte this by hand?

apple_pi
Best Response
You've already chosen the best response.
0
yes

apple_pi
Best Response
You've already chosen the best response.
0
why did you go into radians?

apple_pi
Best Response
You've already chosen the best response.
0
so what is x equal to?

tukajo
Best Response
You've already chosen the best response.
0
I fluttered that up ignore me.

tukajo
Best Response
You've already chosen the best response.
0
Hopefully zrocker can help you X_X

Callisto
Best Response
You've already chosen the best response.
3
\[sin^2(54)+cos^2(72)\]\[=(cos(9054))^2+cos^2(72)\]\[=cos^2(36)+cos^2(72)\]
That looks nicer

apple_pi
Best Response
You've already chosen the best response.
0
Oh, wait... let me try now

Callisto
Best Response
You've already chosen the best response.
3
Okay :

apple_pi
Best Response
You've already chosen the best response.
0
cos^2(36) + (2cos^2(36)1)^2

apple_pi
Best Response
You've already chosen the best response.
0
am i right?

Callisto
Best Response
You've already chosen the best response.
3
Yes.

apple_pi
Best Response
You've already chosen the best response.
0
now... do we evaluate cos(36) or simplify more?

Callisto
Best Response
You've already chosen the best response.
3
Evaluate.

apple_pi
Best Response
You've already chosen the best response.
0
ok. is this straightforward or something we fancily work out?

Callisto
Best Response
You've already chosen the best response.
3
very fancy :

Callisto
Best Response
You've already chosen the best response.
3
let x = 36
5x = 180
3x = 180  2x
sin 3x = sin2x
3 sinx  4sin^3 x = 2sinx cox
Since sinx =/= 0
3 4 sin^2 x = 2cosx
3 4 ( 1cos^2 x) = 2 cos x
4 cos^2 x  2cosx 1 =0
Now, solve for cosx.

zzr0ck3r
Best Response
You've already chosen the best response.
0
wow

Callisto
Best Response
You've already chosen the best response.
3
@apple_pi Come back :'(

zzr0ck3r
Best Response
You've already chosen the best response.
0
So in what class do we learn to play with this trick?

Callisto
Best Response
You've already chosen the best response.
3
I'm sorry, I don't know. I'm not from the US. But for me, I learnt it two years before university.

apple_pi
Best Response
You've already chosen the best response.
0
Sorry... I had to go for a while

apple_pi
Best Response
You've already chosen the best response.
0
Yeah that solved it! Thanks @Callisto

