SOLUTION: If σ is an angle in the third quadrant and csc σ = - 13/5, find the value for 3sin^2 σ-2cos σ as a fraction with no decimals.

Algebra ->  Trigonometry-basics -> SOLUTION: If σ is an angle in the third quadrant and csc σ = - 13/5, find the value for 3sin^2 σ-2cos σ as a fraction with no decimals.      Log On


   

Question 1186336: If σ is an angle in the third quadrant and csc σ = - 13/5, find the value for 3sin^2 σ-2cos σ as a fraction with no decimals.
Answer by robertb(5830) About Me  (Show Source):
You can put this solution on YOUR website!
csc σ = - 13/5 ===> sin%28sigma%29+=+-5%2F13
===> cos%5E2%28sigma%29+=+1+-+sin%5E2%28sigma%29+=+1+-+%28-5%2F13%29%5E2+=+144%2F169

===> cos%28sigma%29+=+-12%2F13. (Cosine is negative over the 3rd quadrant.)

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