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#1 2012-10-26 20:54:41
- Ronald
- Guest
Phi in trigonometry
During class I faced a problem- cos^4(x)+cos^2(x)=1,my friend told me that x=acos(sqrt(phi-1)).when I checked it using calculator,it was correct.how is phi involved in this,please explain.
#2 2012-10-26 21:02:56
- bobbym
- Administrator
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Re: Phi in trigonometry
Hi Ronald;
You make the substitution y = cos(x) and then solve.
Another substitution, u=y^2.
Now it is easy.
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.
#5 2012-10-26 22:05:51
- bobbym
- Administrator
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Re: Phi in trigonometry
Please check your work I am not getting that. For one root I am getting.
That is what you wanted to show.
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 2012-10-27 00:26:51
- bobbym
- Administrator
Offline
Re: Phi in trigonometry
Yes, it is the same but there is no reason to convert to decimal. You should avoid unnecessary simplifications. The way it is done in post #5 is fine.
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.