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#1 2013-03-23 16:48:35

Agnishom
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Trigonometric Equation

If in a triangle,



Then,
What is the value of sin angle A?

Is it 8/27?


'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'
'Who are you to judge everything?' -Alokananda

#2 2013-03-23 19:20:56

bob bundy
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Re: Trigonometric Equation

hi Agnishom

How did you get that?  It's not what I'm getting.

Here's my method.

SINE RULE is:



So I put



and re-arranged to get



Different values of k will make different sized circles but all the resulting triangles will be similar => same three angles.

So it is ok to take a = √6,   b = 2√2,     c = 3√3

Use the cosine rule to get cosA and hence sinA.

I made it



Bob


You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

#3 2013-03-23 19:38:29

Agnishom
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Re: Trigonometric Equation

bob bundy wrote:

hi Agnishom

SINE RULE is:



So I put



and re-arranged to get

I have the following doubts:

I. How did you do the rearrangement?
II. How do you know what to put for a?


'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'
'Who are you to judge everything?' -Alokananda

#4 2013-03-23 19:56:16

Agnishom
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Re: Trigonometric Equation

Okay thanks I managed to understand this

http://img707.imageshack.us/img707/5754/lawofsines.png


'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'
'Who are you to judge everything?' -Alokananda

#5 2013-03-23 22:07:06

bob bundy
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Re: Trigonometric Equation

hi Agnishom,

Glad you understand it.  Your method and mine are essentially the same; I used k; you have t; and then I let k=1.  In yours the t cancels out. 

Bob


You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

#6 2013-03-24 01:29:38

Agnishom
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Re: Trigonometric Equation

smile Yeah Thanks! I had difficulty understanding the cancellation


'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'
'Who are you to judge everything?' -Alokananda

#7 2013-03-24 05:09:28

bob bundy
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Re: Trigonometric Equation

Two triangles with sides in the same ratio are similar.  So the angles are the same.  Therefore you can just call t = 1 without losing any of the problem's conditions.

That's why it cancels out of the cosine rule step.

Bob


You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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