Results 1 to 3 of 3

Math Help - Finding angles in a right angled triangle where one angle is 1/x or x^2

  1. #1
    Newbie
    Joined
    Mar 2011
    Posts
    4

    Finding angles in a right angled triangle where one angle is 1/x or x^2

    Working with a right angled triangle ABC with C as the right angle;
    If A = x and B = x^2
    What are the values of A and B?
    Also,
    If A = x and B = 1/x
    What are the values of A and B?
    Obviously
    A + B + 90 = 180
    So A + B = 90
    So
    x + x^2 = 90
    and
    x + 1/x = 90
    The book I am working with has the answers in the back, so I know the answers, but I don't understand how the answers were arrived at.

    I can work out x + 2x = 90
    3x = 90
    x = 90/3
    x = 30
    2x = 60
    But I don't know the way to do the same with the reciprocal and the square:
    x + 1/x = 90
    1/x = 90 - x which cannot be right.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Grand Panjandrum
    Joined
    Nov 2005
    From
    someplace
    Posts
    14,972
    Thanks
    4
    Quote Originally Posted by PhilC View Post
    Working with a right angled triangle ABC with C as the right angle;
    If A = x and B = x^2
    What are the values of A and B?
    Also,
    If A = x and B = 1/x
    What are the values of A and B?
    Obviously
    A + B + 90 = 180
    So A + B = 90
    So
    x + x^2 = 90
    and
    x + 1/x = 90
    The book I am working with has the answers in the back, so I know the answers, but I don't understand how the answers were arrived at.

    I can work out x + 2x = 90
    3x = 90
    x = 90/3
    x = 30
    2x = 60
    But I don't know the way to do the same with the reciprocal and the square:
    x + 1/x = 90
    1/x = 90 - x which cannot be right.
    x^2+x-90=0 is a quadratic, use what ever method you have been taught to solve quadratics.

    x+\frac{1}{x}=90 multiply through by $$x to get x^2-90x+1=0 which is a quadratic ...

    CB
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Mar 2011
    Posts
    4
    Thanks! Now I just need to remind myself of how to solve quadratics.

    I'm just trying to relearn all my maths from school, and each time I hit a block it sends me down a completely different line of research. It's great this maths stuff, isn't it!
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 1
    Last Post: July 11th 2011, 11:59 PM
  2. Finding angles in a triangle.
    Posted in the Trigonometry Forum
    Replies: 6
    Last Post: February 5th 2010, 05:30 AM
  3. Finding angles in a triangle and a circle.
    Posted in the Trigonometry Forum
    Replies: 2
    Last Post: February 4th 2010, 06:13 PM
  4. Proving Right-Angled/Right Angle Triangle Help
    Posted in the Geometry Forum
    Replies: 3
    Last Post: January 13th 2010, 05:57 AM
  5. Finding angles in a right triangle
    Posted in the Geometry Forum
    Replies: 5
    Last Post: September 13th 2008, 08:44 AM

Search Tags


/mathhelpforum @mathhelpforum