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Homework Help: Trig identities (I think?) for precalc review

  1. Sep 22, 2016 #1
    1. The problem statement, all variables and given/known data
    My calc class is having me review precalc(which i'm really rusty on...)

    21. Find sin θ, sec θ, and cot θ if tan θ = 27
    22. Find sin θ, cos θ, and sec θ if cot θ = 4.
    23. Find cos 2θ if sin θ = 15
    24. Find sin 2θ and cos 2θ if tan θ = √2
    25. Find cos θ and tan θ if sin θ = 0.4 and π/2 ≤ θ < π.
    26. Find cos θ and sin θ if tan θ = 4 and π ≤ θ < 3π/2.

    2. Relevant equations

    3. The attempt at a solution
    I'm not going to ask you to do these for me, but since it's been several years since I've done any of this stuff(that i really do hate!) please refer me to videos / tutorials on how to work with them. My textbook only goes through one problem and that's it. The explanations are not the greatest as well.

    Thanks alot. I apologize for not giving an attempt but all my attempts are so horribly off it's not even worth showing.
  2. jcsd
  3. Sep 22, 2016 #2


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    Do show your attempts.
  4. Sep 22, 2016 #3


    Staff: Mentor

    This one makes no sense. ##-1 \le \sin \theta \le 1##.
  5. Sep 26, 2016 #4
    It was meant to be sinx = 1/5. I've solved all the original question, they were a bit easier than I had imagined.

    Should I still post the solutions or can I mark this question as solved and move on?
  6. Sep 26, 2016 #5


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    Homework Helper
    Gold Member

    Probably either is fine. See what others say.

    Was #21 supposed to have 2/7 rather than 27?
  7. Sep 29, 2016 #6
    Yeah, it was 2/7. Not sure why they turned the way they did when I had copy pasted them
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