Results are out! Find what you need...fast. Get quick advice or join the chat
Hey there Sign in to join this conversationNew here? Join for free

Triangle

Announcements Posted on
    • Thread Starter
    • 0 followers
    Offline

    ReputationRep:
    Given the three points A (3,4,0) , B (8,0,6) , C (0,5,12) in space . find
    1)Area of the triangle ABC
    2)the length of the three medians of this triangle
    3)The measure of the angle ABC
    4)Equation of the plane ABC
    • 2 followers
    Offline

    ReputationRep:
    what have you done so far?
    • 1 follower
    Online

    ReputationRep:
    At least try it before coming on tsr with your homework questions... Why should we do it for you?
    • Thread Starter
    • 0 followers
    Offline

    ReputationRep:
    "Sigh" this is not a homework
    • Thread Starter
    • 0 followers
    Offline

    ReputationRep:
    I found 4) and 1) i need just a little hint for 2) and 3)
    • 2 followers
    Offline

    ReputationRep:
    again, what have you done so far?

    i have no idea what 2) is asking.
    hint for q3 = cosine rule
    • Thread Starter
    • 0 followers
    Offline

    ReputationRep:
    For 1)
    • 3 followers
    Offline

    ReputationRep:
    (Original post by MAA_96)
    2)the length of the three medians of this triangle
    Start by finding the coordinates of the centroid...

    You should know what to do next.

    If not:

    Spoiler:
    Show

    Call the centroid I(a,b,c).

    Median from A:\;\dfrac{3}{2}AI

    Median from B:\;\dfrac{3}{2}BI

    Median from C:\;\dfrac{3}{2}CI
    • Thread Starter
    • 0 followers
    Offline

    ReputationRep:
    (Original post by z0tx)
    Start by finding the coordinates of the centroid...
    Do i have to use midpoint and use the distance formula or...to find that ?
    • 3 followers
    Offline

    ReputationRep:
    (Original post by MAA_96)
    Do i have to use midpoint and use the distance formula or...to find that ?
    Nope, midpoints would be a waste of time.

    The coordinates of the centroid are:

    I\left(\dfrac{1}{3}(x_a+x_b+x_c)  ,\dfrac{1}{3}(y_a+y_b+y_c), \dfrac{1}{3}(z_a+z_b+z_c)\right)

    Keep that in mind for future problems involving triangles!

    Also, in case you don't know: the median is 3/2 of the distance between the vertex in question and the centroid.
    • 3 followers
    Offline

    ReputationRep:
    I should that yes, you could find the three midpoints and calculate the three distances, but why do something thrice when you can do it once?
    • Thread Starter
    • 0 followers
    Offline

    ReputationRep:
    Nice,but why did you choose centroid here?
    • 3 followers
    Offline

    ReputationRep:
    (Original post by MAA_96)
    Nice,but why did you choose centroid here?
    I just told you. Finding the centroid (i.e. a single point) is quicker than finding all the midpoints (i.e. three points).
    • Thread Starter
    • 0 followers
    Offline

    ReputationRep:
    Alright,thank you.

Reply

Submit reply

Register

Thanks for posting! You just need to create an account in order to submit the post
  1. this can't be left blank
    that username has been taken, please choose another Forgotten your password?
  2. this can't be left blank
    this email is already registered. Forgotten your password?
  3. this can't be left blank

    6 characters or longer with both numbers and letters is safer

  4. this can't be left empty
    your full birthday is required
  1. By joining you agree to our Ts and Cs, privacy policy and site rules

  2. Slide to join now Processing…

Updated: June 9, 2012
New on TSR

Find out what year 11 is like

Going into year 11? Students who did it last year share what to expect.

Article updates
Reputation gems:
You get these gems as you gain rep from other members for making good contributions and giving helpful advice.