Reviewing Trigonometry for Quadrant II: Sinθ When Cosθ = -1/4

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SUMMARY

The discussion focuses on finding the value of sinθ given that cosθ = -1/4 and θ is located in Quadrant II. Participants emphasize the importance of the unit circle and the fundamental identity sin²θ + cos²θ = 1 for solving the problem. Drawing a right triangle and visualizing the relationships between sine and cosine is recommended as an effective strategy. The insights shared by users Mark and Sammy highlight the value of collaborative learning in mastering trigonometric concepts.

PREREQUISITES
  • Understanding of the unit circle and its significance in trigonometry
  • Familiarity with the fundamental trigonometric identity sin²θ + cos²θ = 1
  • Basic knowledge of right triangle properties and definitions of sine and cosine
  • Ability to identify the signs of trigonometric functions in different quadrants
NEXT STEPS
  • Review the unit circle and its application in solving trigonometric equations
  • Practice using the fundamental identity sin²θ + cos²θ = 1 with various cosine values
  • Explore the properties of trigonometric functions in different quadrants
  • Draw and analyze right triangles to reinforce understanding of sine and cosine relationships
USEFUL FOR

Students studying trigonometry, educators teaching trigonometric concepts, and anyone needing to reinforce their understanding of sine and cosine in Quadrant II.

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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 :)
 
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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.
 


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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