Quandaries and Queries
  

 

im trying to verify this identity:

sin(x)+sin(5x)
-------------------- = tan(3x)
cos(x)+cos(5x)

ive gotten as far as making tan to = sin over cos, but still what am i
supposed to do?
my book is worthless when it comes to identities...

thanks
patrick
 

 

Hi Patrick,

There is an identity that turns sums into products:

sin A + sin B = 2 sin((A+B)/2) cos((A-B)/2)

and

cos A + cos B = 2 cos((A+B)/2) cos((A-B)/2)

Chris

 
 

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