Trig identities

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wallflower#1
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#1
Report Thread starter 7 years ago
#1
Hi there guys,
Please can someone help with trigonometric identity...
1/1+sin*2x + 1/1-sin*2x = 2/cos*2x

Thnx!!
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lazy_fish
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#2
Report 7 years ago
#2
(Original post by wallflower#1)
...
Be careful copying down the question. Pretty sure the trigonometric identity is

 \displaystyle \frac {1}{1+\sin 2x} + \frac {1}{1-\sin 2x} = \frac {2}{\cos^2 2x}

Anyway, show attempt? Try combining two fractions into one.

Good luck.
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wallflower#1
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#3
Report Thread starter 7 years ago
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(Original post by velvetcap)
Do you mean \frac{1}{1+\sin 2x}+\frac{1}{1-\sin 2x}=\frac{2}{\cos 2x}?
yes,..... we've just started this topic in class. What's the first thing we need to do??
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wallflower#1
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#4
Report Thread starter 7 years ago
#4
(Original post by velvetcap)
Add the fractions, like \frac{a}{b}+\frac{c}{d}=\frac{ad+bc}{ad}. So \frac{1-\sin 2x+1+\sin 2x}{(1-\sin 2x)(1+\sin 2x)}=\frac{2}{1-\sin ^2 2x} where we used difference of squares in the denominator. Now use 1-\sin ^2 2x=\cos^2 2x to get \frac{2}{\cos^2 2x}. It appears the question was what lazy_fish proposed.
Thank you =)...yes ur right, but i didn't exactly know what to still do
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wallflower#1
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#5
Report Thread starter 7 years ago
#5
(Original post by lazy_fish)
Be careful copying down the question. Pretty sure the trigonometric identity is

 \displaystyle \frac {1}{1+\sin 2x} + \frac {1}{1-\sin 2x} = \frac {2}{\cos^2 2x}

Anyway, show attempt? Try combining two fractions into one.

Good luck.
thanks :-)
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