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Solving a trig equation for x

  • Thread starter Wessssss
  • Start date
  • #1
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Homework Statement


cos^2x+2sin^2x=-1

Solve for x

Homework Equations





The Attempt at a Solution


I don't really know how to start. I know cos^2x+sin^2x=1 but I don't think I can apply that with the 2 thrown in there.
 

Answers and Replies

  • #2
SteamKing
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Observe: cos^2 + 2 sin^2 = (cos^2 + sin^2) + sin^2
 
  • #3
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thank you
 
  • #4
HallsofIvy
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Or, if it weren't quite that obvious, you could have replaced [itex]cos^2(x)[/itex] with [itex]1- sin^2(x)[/itex]. That is, [itex]cos^2(x)+ 2sin^2(x)= (1- sin^2(x))+ 2sin^2(x)= 1+ sin^2(x)= 1.
 

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