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aussy123

  • 3 years ago

Write the following expression as a function of a positive acute angle. cos 125

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  1. terenzreignz
    • 3 years ago
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    @aussy123 It might help you to know that with your angle in degrees, \[\large \cos \ \theta = \sin (90^o - \theta) \]

  2. terenzreignz
    • 3 years ago
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    So \[\large \cos(125^o)=\sin(90^o - 125^o)=\sin(-35^o)\]

  3. aussy123
    • 3 years ago
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    why did you use sin

  4. terenzreignz
    • 3 years ago
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    It's an identity. It didn't say to use a specific function, it just says use a function.

  5. aussy123
    • 3 years ago
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    oh sorry

  6. terenzreignz
    • 3 years ago
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    Get it now?

  7. aussy123
    • 3 years ago
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    yes a little

  8. aussy123
    • 3 years ago
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    the answer is -cos55

  9. terenzreignz
    • 3 years ago
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    I suppose so. You're right :) It stems from the fact that it's equal to sin(-35) = -sin(35) = -cos(90 - 35)

  10. aussy123
    • 3 years ago
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    I tried that way too, but I also did cos 125 = cos (180 - 125) = - cos 55

  11. terenzreignz
    • 3 years ago
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    Well, as long as your methods are valid, it should be no problem.

  12. aussy123
    • 3 years ago
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    Thank you!

  13. terenzreignz
    • 3 years ago
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    No problem :)

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