Results 1 to 10 of 10

Math Help - Geometry question

  1. #1
    Junior Member
    Joined
    Jun 2013
    From
    Ireland
    Posts
    43

    Geometry question

    HI,
    I AM AFRAID THE ATTACHED QUESTION, WHICH I HOPE YOU CAN OPEN, HAS ME STUMPED A LITTLE.
    I WOULD WELCOME ANY SUGGESTIONS THAT YOU MAY HAVE.
    THANKING YOU IN ADVANCE AND HAVE A GOOD WEEKEND,
    SHANE.

    THE ANSWER TO PART (ii) OF THE QUESTION IS \frac{a^2\sqrt{3}}{3}
    Attached Files Attached Files
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor

    Joined
    Apr 2005
    Posts
    15,365
    Thanks
    1311

    Re: Geometry question

    A few tips for the future- do NOT use all caps- it makes it look like you are "yelling". As much as possible, type what your problem is- many people will not open attached files- there is always a danger of a computer virus. Finally, if this problem has stumped you "a little" then you must have tried something. Show what you have tried so we will know better what hints will help.

    Now, as for this problem- you have two right triangles where the hypotenuse of one is a leg of the other. The result you want involves cosines of two of the angles. I would start by assigning labels to each side, write out the definition of "cosine" in terms of the sides and stare at them until inspiration hits.
    Last edited by HallsofIvy; August 2nd 2013 at 09:27 AM.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Super Member
    Joined
    Nov 2007
    From
    Trumbull Ct
    Posts
    904
    Thanks
    27

    Re: Geometry question

    Hello Seanboy,
    Do you know the properties of an isosceles right triangle and those of a 30-60 right triangle? You should and the answer is a one minute snap.
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Junior Member
    Joined
    Jun 2013
    From
    Ireland
    Posts
    43

    Re: Geometry question

    Hello,
    I take your meaning.
    Thanks for taking the time to reply.
    Shane.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Junior Member
    Joined
    Jun 2013
    From
    Ireland
    Posts
    43

    Re: Geometry question

    Hello,
    If we want to get pedantic, by "a little", I actually meant "a lot".
    I feel like a schoolboy who has just been chastised by a teacher.
    As I wipe the tears away, I would like to thank you for taking the time to reply.
    Your advice is well taken and much appreciated.
    THANK YOU,
    Shane.
    Follow Math Help Forum on Facebook and Google+

  6. #6
    Super Member
    Joined
    Jul 2012
    From
    INDIA
    Posts
    826
    Thanks
    209

    Re: Geometry question

    Geometry question-03-aug-13.png
    Follow Math Help Forum on Facebook and Google+

  7. #7
    MHF Contributor

    Joined
    Apr 2005
    Posts
    15,365
    Thanks
    1311

    Re: Geometry question

    Quote Originally Posted by Seaniboy View Post
    Hello,
    If we want to get pedantic, by "a little", I actually meant "a lot".
    I feel like a schoolboy who has just been chastised by a teacher.
    As I wipe the tears away, I would like to thank you for taking the time to reply.
    Your advice is well taken and much appreciated.
    THANK YOU,
    Shane.
    Oh, I got chastised by teachers a lot. I never "wiped the tears away", I just wiped the teacher away!

    In any case, were you able to do this problem? (Before ibdutt gave you the answer.)
    Follow Math Help Forum on Facebook and Google+

  8. #8
    Junior Member
    Joined
    Jun 2013
    From
    Ireland
    Posts
    43

    Re: Geometry question

    Wipe the teacher away - It may be a while before I am up to that level.
    Yes, I worked out the answer, thanks. I only got back to work out the question after I had received the three replies.
    All very helpful and insightful. You kindly gave me the template and Ibdutt filled in the blanks.
    As Bjhopper pointed out for the second part of the question, it is surprising how I let slip the qualities of 45-45-90 and 30-60-90 triangles.
    Thanks once again for your help.
    Follow Math Help Forum on Facebook and Google+

  9. #9
    Junior Member
    Joined
    Jun 2013
    From
    Ireland
    Posts
    43

    Re: Geometry question

    Thanks so much for your reply and for working the problem out for me.
    Follow Math Help Forum on Facebook and Google+

  10. #10
    Super Member
    Joined
    Nov 2007
    From
    Trumbull Ct
    Posts
    904
    Thanks
    27

    Re: Geometry question

    Hello Shane,
    I am sorry that my reply upset you. All I wanted to tell you and other parties is that solution of special rt triangles is easy if you know the rules.Using Pythagorean theorem or trig is not best.Following are my solutions to part 1 and 2.

    Part 1 Label triangles as follows 45 deg tri a,a,c other rt tri c,d,b b is hypot and d is opposite angle y

    c = a rad2 property of 45 deg rt tri
    cosx =1/2 c /a adj over hyp = 1/2 a rad2/a =rad2/2
    cos y =c/b adj over hyp=arad2/b
    cosx*cosy = rad2/2*arad2/b = a/b
    b= a/cosx*cosy

    Part 2
    c= arad2
    d= arad2/rad3 property of 30 deg rt tri
    area pqs c*d*1/2 =(arad2)^2/2rad3=2a^2/2rad3=a^2/rad3 = a^2*rad3 /rad3^2 =a^2rad3/3
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. SAT Geometry Question
    Posted in the Geometry Forum
    Replies: 12
    Last Post: July 17th 2013, 02:51 PM
  2. Geometry Question
    Posted in the Differential Geometry Forum
    Replies: 1
    Last Post: February 8th 2011, 01:34 PM
  3. Geometry Question
    Posted in the Geometry Forum
    Replies: 1
    Last Post: December 2nd 2008, 01:09 PM
  4. Replies: 6
    Last Post: August 18th 2007, 12:13 PM
  5. Geometry Question
    Posted in the Geometry Forum
    Replies: 5
    Last Post: March 1st 2007, 05:06 PM

Search Tags


/mathhelpforum @mathhelpforum