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Homework Help: Basic trignometry

  1. Jun 20, 2014 #1
    1. The problem statement, all variables and given/known data
    Let f(θ)=cotθ/1+cotθ and α+β=5π/4
    then the value of f(α).f(β) is:

    3. The attempt at a solution
    (cotα/1+cotα)* (cotβ/1+cotβ)

    = cotα.cotβ/((1+cotα)(1+cotβ))
    Last edited: Jun 20, 2014
  2. jcsd
  3. Jun 20, 2014 #2


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    Staff: Mentor

    Hi suresh. http://img96.imageshack.us/img96/5725/red5e5etimes5e5e45e5e25.gif [Broken]

    Was there supposed to be an accompanying question?

    When you have an answer, you could always check it by taking any value for α then using your calculator.....

    Double-check by taking another value. :smile:

    Also, your expressions above appear to be invalid, owing to a dearth of essential brackets. To help you fix this, please accept some spares I happen to have lying around: (((((((((())))))))) :wink:
    Last edited by a moderator: May 6, 2017
  4. Jun 20, 2014 #3


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    You should be looking for relevant trigonometric identities, sum- of-angles identities, and the law of tangents.
  5. Jun 20, 2014 #4
    Thanks for all the help guys sorry for not writing clearly if only I knew how to put fractions
    Also sorry for using some other symbol which I thought was pi and confusing all of you
  6. Jun 20, 2014 #5


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    Staff: Mentor

    You mean like this? Let f(θ)=cotθ/(1+cotθ)

    Whatever the symbol was that you originally used, I read it as Pi. :smile:
  7. Jun 20, 2014 #6


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    You get
    $$ f(\theta) = \frac{\cot\theta}{1 + \cot\theta} $$
    by typing "f(\theta) = \frac{\cot\theta}{1 + \cot\theta}" in TeX mode. You get TeX mode by either putting your equation inside double dollar signs or inside tex tags.
  8. Jun 20, 2014 #7

    Ray Vickson

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    Science Advisor
    Homework Helper

    Doing fractions is easy: if you have just ##\frac{a}{b}## it is sufficient to type a/b. If you have something like ##\frac{a}{b+c}## then you absolutely must use parentheses, but it is easy also: just type a/(b+c).
  9. Jun 21, 2014 #8


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    Gold Member

    I recommend you to use latex all the time.

    You only have to write \pi for ##\pi##
    And \frac{a}{b} for ##\frac{a}{b}##

    Use two # signs between the latex code to render it inline.
    Use two $ signs between the latex code to render it indented and on a separate line. This can be useful for writing large equations which are rendered stupidly using two #.
  10. Jun 21, 2014 #9
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