SRL Archive - Mathematics

Trigonometry (With reward)

Main

2010-01-08 16:51:44

The second question is asking you to find the value of sin of 157.5 degrees using double angle formulas
The person solve most of these correctly gets
Option:
1)Me buy junk (1.5 mil)
2)Me gold farm (1 mil)
3)Me get you 1mil fletch exp

Gu3st...

2010-01-08 18:34:58

1) sin(3a)
2) ???

1) 2 (cos^2(3 x)-sin(2 x) sin(3 x)) = (-(2 n)/5<=x<=(2 n)/5)
2) 6 sin^2(x)+sin(x)-2 = 0 x = pi/6

All I did was to play around with wolframalpha, so these answers are most likely false, but some of them looks like they are correct

Main

2010-01-08 23:36:41

The second question is in degrees and we were suppose to find its value from double angle formula

mormonman

2010-01-09 00:39:41

I'm pretty sure most of these are easily done with identities. You just got to be able to find where to use them.

Micro

2010-01-09 09:13:06

I doubt anybody who hasn't done A-level/University level maths could answer that(so the person who'll answer your question is probably over the age of 17)….Also, why not post a simple question for beginners?

Main

2010-01-09 09:35:33

This is my review questions which I needed to handed it in on monday for credit:(
which is why I am offering rewards

mixster

2010-01-09 10:29:13

Sorry to be offtopic, but I find this topic hugely ironic considering your sig link to a site promoting videos that help teach maths (etc and to my knowledge).

Gu3st...

2010-01-09 10:34:08

From: mixster
Sorry to be offtopic, but I find this topic hugely ironic considering your sig link to a site promoting videos that help teach maths (etc and to my knowledge).

Lol! xD I didn't notice :)

And ask someone extremely smart people, Naum, Markus, Boreas, Wizzup?, WT, dr tara etc etc

Main

2010-01-09 12:33:59

That website isn't really made for AP stuff :(

Santa_Clause

2010-01-10 03:11:57

Question 1, first set:

$\\ CosaSin2a + Cos2aSina = Sin(2a + a) = Sin3a$
Question 2 of the first set:

$\\Cos 315 = Cos 45 = \frac{1}{\sqrt{2}} \\ Cos 315 = 1 - 2Sin^{2}157.5 \\ 1 - 2Sin^{2}157.5 = \frac{1}{\sqrt{2}} \\ Sin^{2}157.5 = \frac{1}{2}(1 - \frac{1}{\sqrt{2}}) \\ Sin 157.5 = \sqrt{\frac{\sqrt{2} - 1}{2\sqrt{2}}}$
Question 1 of the second set, which I think should be Cos3xCos2x not Cos3xCos3x:

$\\ 2(Cos 3xCos 2x - Sin3xSin2x) = 1 \\ 2Cos(3x + 2x) = 1 \\ Cos 5x = 0.5, -2\pi \leq 5x \leq 2\pi \\ 5x = \frac{\pi}{3}, \frac{5\pi}{3} \\ x = \frac{\pi}{15}, \frac{\pi}{3} \\$
Question 2 of the second set, I've stopped at where it should be easy, just using the calculator to find values of x:

$\\ 6Sin^{2}x + Sin x - 2 = 0 \\ (3Sinx + 2)(2Sinx - 1) = 0 \\ Sin x = \frac{-2}{3}, \frac{1}{2}\\$
And that final question:

$\\ Cos^{2}\frac{x}{4}Cos\frac{x}{3} + 2Sin\frac{x}{4}Cos\frac{x}{4}Sin\frac{x}{3} - Sin^{2}\frac{x}{4}Cos\frac{x}{3} = \\ (Cos^{2}\frac{x}{4} - Sin^{2}\frac{x}{4})Cos\frac{x}{3} + (2Sin\frac{x}{4}Cos\frac{x}{4})Sin\frac{x}{3}=\\ Cos\frac{x}{2}Cos\frac{x}{3} + Sin\frac{x}{2}Sin\frac{x}{3}=\\ Cos(\frac{x}{2}-\frac{x}{3}) = Cos\frac{x}{6}$
Enjoy.

Main

2010-01-10 03:45:38

Congratulations:) Yeah it was cos3xcos2x
Lets discuss the rewards of pm.

Two last thing

I got 7/25 but can any one check? I've left out my steps because I don't want it to be misleading if it had a error in it.

sinx=-2/3
How would you show steps if you were asked?

Santa_Clause

2010-01-10 07:14:15

From: Main_Ftw
Congratulations:) Yeah it was cos3xcos2x
Lets discuss the rewards of pm.

Two last thing
I got 7/25 but can any one check? I've left out my steps because I don't want it to be misleading if it had a error in it.

sinx=-2/3
How would you show steps if you were asked?

7/25 is correct.

And you don't really need to show steps for Sin x = -2/3, since it's just some calculator work.

Oh and, I don't want a reward, thanks though.

Gu3st...

2010-01-10 07:46:43

Santy is a real gentleman :)
And what's up with posting once per month?

Main

2010-01-10 07:50:30

Thanks again for your help.
If you need $$ in the future, pm me.

Santa_Clause

2010-01-11 06:53:56

From: Zyt3x
Santy is a real gentleman :)
And what's up with posting once per month?

Haha thankyou :) And I just don't feel that I have much to say anymore, I post when I can be of help or when I have some useful insight.

From: Main_Ftw
Thanks again for your help.
If you need $$ in the future, pm me.

No problem, and thankyou.

Main

2010-01-11 17:07:44

What is your highest education level santa?

Gu3st...

2010-01-11 17:16:44

From: Main_Ftw
What is your highest education level santa?

HIGH.
sorry, I just had to. Santy is brilliant :O

Main

2010-01-11 17:51:23

Prolly Ph.D:)

We run u.s.

2010-01-11 18:27:36

LOL Ph.D. I bet he is.
He said simple calculator work…

Main

2010-01-11 18:38:15

Thats the rest.
Besides, answer doesn't matter, its the steps:)

Santa_Clause

2010-01-12 00:09:22

From: Main_Ftw
What is your highest education level santa?

Haha…I'm only 15 and 2 months old, so I haven't finished high school yet :p

Main

2010-01-12 00:40:12

Dang, how did you know these stuff lol? I am in grade 12…

Santa_Clause

2010-01-12 00:58:46

I finished high-school maths (and came first in NSW in one maths subject, second in the other)…because I like it :D

Main

2010-01-12 01:02:11

Were you ever on the news?

Santa_Clause

2010-01-12 01:05:01

From: Main_Ftw
Were you ever on the news?

I was in the newspaper.

Main

2010-01-12 01:07:36

Genius:)

Did they ever publish it online? If they did, do you mind post the link?

Santa_Clause

2010-01-12 01:13:20

Can be found here.

I'm Samuel Tawfik, second from the right.

vcvv

2010-01-12 07:02:42

Awesome! Didn't know you guys were that young, :D

Johura

2010-01-12 08:09:58

From: Santa_Clause
Can be found here.

I'm Samuel Tawfik, second from the right.

<offtopic>
ZZOOMG, I remember you, didn't we used to talk on msn?
</offtopic>

Santa_Clause

2010-01-12 20:51:24

From: Johura
<offtopic>
ZZOOMG, I remember you, didn't we used to talk on msn?
</offtopic>

If you're the person that was called Jahuro, then yes :p

Johura

2010-01-12 21:12:28

I'm Johura, his evil twin brother.

Santa_Clause

2010-01-13 07:57:39

From: Johura
I'm Johura, his evil twin brother.

Then I have probably talked to you on MSN before :D