Trigonometry question. Find the value of sinθ if cosθ=−1/4 and θ is in Quadrant II

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nukeman
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Homework Statement



Question: Find the value of sinθ if cosθ=−1/4 and θ is in Quadrant II

I have not done TRIG in a long time. Given this question, what should I read over/review ? I don't remember how to solve these types of questions?

Homework Equations





The Attempt at a Solution



Not sure what kind of attempt I can do... I have to memorize the unit circle correct?

P.S. - Thanks to Mark an Sammy for recent help - Got 93% on my first of 3 midterms :)
 

Answers and Replies

  • #2
hotvette
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Might be good to draw a picture and remember the definition of cos in terms of lengths of sides of a right triangle. That should get you going in the right direction.
 
  • #3
LCKurtz
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Drawing a picture as hotvette suggests is an excellent idea. Another way is to use the fundamental identity ##\sin^2\theta + \cos^2\theta = 1## to solve for the cosine. The quadrant will help you choose the sign.
 

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