Friday, September 29, 2017

trigonometry - How to prove that cscx2cosxcot2x=2sinx



My idea was...




LHS=1sinx2cosxtan2x=tan2xsin2xsinxtan2x



from here, I don't know how to continue, please help! thanks



ps, please teach me how to use the "divide" symbol



Answer



Somewhere you'll need a double-angle formula:
tan(2x)=2tanx1tan2x
or
tan(2x)=sin(2x)cos(2x)=2sinxcosxcos2xsin2x.


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