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#1 2009-08-16 16:40:09
- Fla$h
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Trigonometry Proofs
Hi Guys,i hope im posting in the right forum.Here Are A Few Exercises:-
PROVE THE FOLLOWING:-
1)
2)
3)
4)
5)
6)
I got these out of a maths textbook
#2 2009-08-16 17:56:07
- bobbym
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Re: Trigonometry Proofs
Hi Fla$h;
For #1)
Cross multiply and we have.
Last edited by bobbym (2009-08-16 18:04:19)
In mathematics, you don't understand things. You just get used to them.
90% of mathematicians do not understand 90% of currently published mathematics.
I am willing to wager that over 75% of the new words that appeared were nothing more than spelling errors that caught on.
#3 2009-08-16 17:57:16
- juriguen
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Re: Trigonometry Proofs
Hi!
I think I got the first one:
1.
Jose
“Make everything as simple as possible, but not simpler.” -- Albert Einstein
#4 2009-08-16 18:04:50
- Identity
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Re: Trigonometry Proofs
Most trig proofs involve converting 'tan' and 'cot' to 'sin' and 'cos', and lots of fractions!
#5 2009-08-16 18:24:00
- yamini
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Re: Trigonometry Proofs
hey i got ans for 4th ques
;)
sinA-2sincubeA/2coscubeA-cosA
take sinA common in numerator and cos A in denominator
we get
sinA(1-2sinsquareA)/cosA(2cossquareA-1)
cos2A formula is 1-2sinsquareA and 2cossquareA-1
so they both will get cancelled
we get
sinA/cosA=tanA
hence proved. 
:P:
#6 2009-08-17 08:25:55
- bobbym
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Re: Trigonometry Proofs
Hi Fla$h;
Here is another way for #4
Last edited by bobbym (2009-08-17 08:26:21)
In mathematics, you don't understand things. You just get used to them.
90% of mathematicians do not understand 90% of currently published mathematics.
I am willing to wager that over 75% of the new words that appeared were nothing more than spelling errors that caught on.
#7 2009-08-17 10:50:25
- bobbym
- Administrator
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Re: Trigonometry Proofs
Hi Fla$h;
for #6
Expand the LHS.
Last edited by bobbym (2009-08-17 10:56:20)
In mathematics, you don't understand things. You just get used to them.
90% of mathematicians do not understand 90% of currently published mathematics.
I am willing to wager that over 75% of the new words that appeared were nothing more than spelling errors that caught on.
#8 2009-08-22 10:01:47
- Fruityloop
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Re: Trigonometry Proofs
Hi Fla$h!;
Here's #2...
using
we get
Last edited by Fruityloop (2009-08-22 10:11:56)
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#9 2009-08-22 12:40:11
- bobbym
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Re: Trigonometry Proofs
Hi Fla$h;
Problem #3 is not an identity.
It should read:
Now here is the proof for #3:
Now cross multiply:
Now substitute cos²(A) = 1- sin²(A) and clean up:
Last edited by bobbym (2009-08-22 14:12:07)
In mathematics, you don't understand things. You just get used to them.
90% of mathematicians do not understand 90% of currently published mathematics.
I am willing to wager that over 75% of the new words that appeared were nothing more than spelling errors that caught on.
#10 2009-08-22 17:45:12
- bobbym
- Administrator
Online
Re: Trigonometry Proofs
Hi Fla$h;
For problem #5
Expanding the LHS and remembering that:
We get:
Now using:
and
We get:
Using:
Last edited by bobbym (2009-08-22 17:48:56)
In mathematics, you don't understand things. You just get used to them.
90% of mathematicians do not understand 90% of currently published mathematics.
I am willing to wager that over 75% of the new words that appeared were nothing more than spelling errors that caught on.