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Simple question about sin, cos , tan

  1. Dec 16, 2009 #1
    No problem specifically, just more of a method question.
    I am extremely confused on when to use sin cos and tan. Say for instance it gives me an angle, say theta, and one side. How would I be able to tell what to use sin cos or tan. I know the trick SohCahToa but I really am confused. I am in a physics class and this comes up all the time and I feel as if I eliminate this barrier it will really benefit me in the long run. Thanks.
  2. jcsd
  3. Dec 16, 2009 #2
    First understand what angle they are talking about. If you know what angle is being measured, then using sohcahtoa you can decide for yourself if sin cos or tan need to be used. If youre confused, draw the problem out to make it easier for you to see which angle is in question.
  4. Dec 16, 2009 #3


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    Hi jamesdubya! :smile:

    Since you know SohCahToa, I don't really understand what the problem is.

    If you're given a right-angled triangle, and the length of the hypotenuse, and they ask you the length of one side, then see if that side is the adjacent side … if it is, you want adjacent/hypotenuse, so that's cos (Cah :wink:), if it's not, you want opposite/hypotenuse, so that's sin (Soh).

    If you find SohCahToa difficult to apply, I suggest you remember that sin0 =tan0 = 0 and cos0 = 1 …

    if you draw a thin triangle, so one angle is nearly 0, it's pretty obvious then which ratios are nearly 0 (so they must be sin and tan), and which is nearly 1 (so that must be cos). :smile:
  5. Dec 16, 2009 #4
    Thank you very much that helps greatly :)
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