Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Problem finding exterior angle

  1. Sep 3, 2011 #1
    1. The problem statement, all variables and given/known data
    Triangle ABC has been inscribed in the circle with center o.E is the midpoint of arc BC.DE is the diameter.E is joined to A, B and C.D is joined to A . If angle ABC =72 degrees and angle ACB = 48 degrees,
    find angle DAC.
    (I have attached the diagram given in book although its not a very good one)

    2. Relevant equations
    -

    3. The attempt at a solution
    In this one what i did was,
    i found angle BAC =(180-72-48)= 60 degrees
    then i tried to subtend angle from the diameter to get 90 degree on the circumference but it did not help.
    and i found the other angles like angle BEA=48 degrees and angle DEC= 72 degrees by the theorem the a chord extend equal angles on the circumference. But i can't get any further than this .Please help.
    the answer given in my book is 60 degrees.
    If I am going wrong somewhere please do let me know.
    Thank you.
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     

    Attached Files:

  2. jcsd
  3. Sep 3, 2011 #2

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    hi 1/2"! :smile:

    use the theorem that opposite angles subtended from the same chord (ie opposite angles of an inscribed quadrilateral) add up to 180° :wink:
     
  4. Sep 3, 2011 #3
    I think i have already done it.
    can you please be alittle more elaborate?
    thanks.:smile:
     
  5. Sep 3, 2011 #4

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    i'm confused … if you've already done it, what's the problem?

    and i've given you the full theorem … what is there to elaborate further? :confused:
     
  6. Sep 3, 2011 #5
    I am really sorry to confuse you.:frown:
    Could you give a more direct clue how to get the angle DAC?
    and i am really sorry.
     
  7. Sep 3, 2011 #6
    Thank you
    but i have got it.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook