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#1 2014-06-06 00:09:12

David
Member
From: Bumpkinland
Registered: 2014-04-23
Posts: 3,137

Trigonometric Equations

Hello everyone,
I need help with trigonometric equations, a link to math is fun would be great. But first, could anyone help me with this question? A step-by-step answer would be great. Thanks in advance.

Solve the following trigonometric equations for

(edited)

Last edited by David (2014-06-06 03:56:39)

Meaningless, meaningless, Everything is meaningless! - Ecclesiastes 1:2

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#2 2014-06-06 00:26:05

Agnishom
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From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,856
Website

Re: Trigonometric Equations

First, you've to transform this into an equation of sines. Then, apply the submultiple angle formulae.

I'll do this once I am back from the bookstore.

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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#3 2014-06-06 00:29:02

David
Member
From: Bumpkinland
Registered: 2014-04-23
Posts: 3,137

Re: Trigonometric Equations

ty

Meaningless, meaningless, Everything is meaningless! - Ecclesiastes 1:2

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#4 2014-06-06 02:35:08

liuv
Member
Registered: 2006-05-14
Posts: 29

Re: Trigonometric Equations

I'm from Beijing China.

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#5 2014-06-06 02:44:39

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,856
Website

Re: Trigonometric Equations

Please post the answer that you originally attached with the first post.

I'm not sure if you want a numerical solution or an exact one.

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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#6 2014-06-06 02:53:51

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: Trigonometric Equations

The 300° is just an approximation is it not?

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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#7 2014-06-06 02:56:08

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,856
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Re: Trigonometric Equations

How did he get 75 there?

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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#8 2014-06-06 03:03:55

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: Trigonometric Equations

I am not sure, but he should replace the = with ≈ in his work.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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#9 2014-06-06 03:54:18

David
Member
From: Bumpkinland
Registered: 2014-04-23
Posts: 3,137

Re: Trigonometric Equations

Wait, I will upload a image.

Meaningless, meaningless, Everything is meaningless! - Ecclesiastes 1:2

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#10 2014-06-06 03:55:23

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: Trigonometric Equations

Hi;

That says 1 / 2 not 1 / 4.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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#11 2014-06-06 03:56:08

David
Member
From: Bumpkinland
Registered: 2014-04-23
Posts: 3,137

Re: Trigonometric Equations

oops...

Meaningless, meaningless, Everything is meaningless! - Ecclesiastes 1:2

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#12 2014-06-06 04:00:56

bob bundy
Registered: 2010-06-20
Posts: 8,382

Re: Trigonometric Equations

using edited version

cos (x/2) = 1/4

Cos2A = 2.cos^2  (A) -1

cos(x) = 2 x (1/4)^2 - 1 = - 7/8

then use acos

Bob

Last edited by bob bundy (2014-06-06 04:02:02)

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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#13 2014-06-06 04:01:58

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,856
Website

Re: Trigonometric Equations

Does using acos give you any exact value?

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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#14 2014-06-06 04:02:49

bob bundy
Registered: 2010-06-20
Posts: 8,382

Re: Trigonometric Equations

no.  I don't think you can get an exact value easily here.

Bob

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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#15 2014-06-06 04:03:59

David
Member
From: Bumpkinland
Registered: 2014-04-23
Posts: 3,137

Re: Trigonometric Equations

Could you explain a little bit? ty.

Meaningless, meaningless, Everything is meaningless! - Ecclesiastes 1:2

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#16 2014-06-06 04:08:23

bob bundy
Registered: 2010-06-20
Posts: 8,382

Re: Trigonometric Equations

sec = 1/cos so invert the equation.

Then use the double angle formula:

The rest is arithmetic.

Bob

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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#17 2014-06-06 04:09:34

David
Member
From: Bumpkinland
Registered: 2014-04-23
Posts: 3,137

Re: Trigonometric Equations

Thanks Bob and everyone. Is the double angle formula on mif?

Meaningless, meaningless, Everything is meaningless! - Ecclesiastes 1:2

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#18 2014-06-06 04:10:43

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,856
Website

Re: Trigonometric Equations

The double angle formula can be derived with the compound angle formula

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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#19 2014-06-06 04:14:12

bob bundy
Registered: 2010-06-20
Posts: 8,382

Re: Trigonometric Equations

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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#20 2014-06-06 04:15:19

bob bundy
Registered: 2010-06-20
Posts: 8,382

Re: Trigonometric Equations

Off-line for a while.  I'll be back.

B

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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#21 2014-06-06 04:16:56

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,856
Website

Re: Trigonometric Equations

These identities are a pain.

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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#22 2014-06-06 19:49:15

liuv
Member
Registered: 2006-05-14
Posts: 29

Re: Trigonometric Equations

bobbym wrote:

The 300° is just an approximation is it not?

I'm from Beijing China.

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