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math writing trignometric expressions in the form Rsin(thetha+alpha) confusion

as title says, suppose you had the expression cos(thetha)+(sqrt3)sin(thetha), how would you know whether you write it in the form Rcos(thetha-alpha) or Rsin(thetha+alpha).. I really don't see why there should be a difference, though when I used Rcos(thetha-alpha) for this particular expression instead of Rsin(thetha+alpha), when solving for costheta+(sqrt3)sinthetha =2.. the answer came out wrong according to ms.
R will.obviously be the same whichever way you do it.

As for choice, unless the question specifies which, there shouldn't be any real difference, especially since the done and cosine curves are a pi/2 translation away from.each other.

Might be wise for you to post piccies of the question, your working and perhaps the MS.

I assume you've got your calculator in the correct angle mode? Has been known :wink:
(edited 1 year ago)
Original post by Abraham_Otaku
as title says, suppose you had the expression cos(thetha)+(sqrt3)sin(thetha), how would you know whether you write it in the form Rcos(thetha-alpha) or Rsin(thetha+alpha).. I really don't see why there should be a difference, though when I used Rcos(thetha-alpha) for this particular expression instead of Rsin(thetha+alpha), when solving for costheta+(sqrt3)sinthetha =2.. the answer came out wrong according to ms.


You should get the same answer - please post the question and your working.

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