Triple angle proof

Skelly4444

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Apr 4, 2019
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26
How can (cos3x / sinx) + (sin3x / cosx) be identically equivalent to 2cot2x

I have tried rewriting everything but cannot seem to get anywhere with this?

Any advice would be greatly appreciated.
 

Dr.Peterson

Elite Member
Joined
Nov 12, 2017
Messages
12,937
How can (cos3x / sinx) + (sin3x / cosx) be identically equivalent to 2cot2x

I have tried rewriting everything but cannot seem to get anywhere with this?

Any advice would be greatly appreciated.
I would first combine it into one fraction. Then I'd recognize something familiar. Something different might work better for you, but we'll know that after we've seen your work.
 

Skelly4444

New member
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Apr 4, 2019
Messages
26
Thanks for responding, I've actually managed to work it out by using common denominator of sinxcosx and then recognising that the top of the fraction is the addition format for cos(3x - x) which obviously equates to cos2x. From here, it was quite straight forward.
 

Subhotosh Khan

Super Moderator
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Jun 18, 2007
Messages
25,870
Thanks for responding, I've actually managed to work it out by using common denominator of sinxcosx and then recognising that the top of the fraction is the addition format for cos(3x - x) which obviously equates to cos2x. From here, it was quite straight forward.
Nice work !!
 
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