Turn on thread page Beta
    • Thread Starter
    Offline

    0
    ReputationRep:
    im really stuck on d, i just cant find out the 2 simulatanious equations,

    i find it much easier when you have to find the one on the axis or when one of the ns are given to you

    pic below



    Offline

    12
    ReputationRep:
     Ucos40 = Vcos70
     Ucos50 + Vcos20 = 5
    its just a matter of simultaneous equations....

    look at the top equation:
     \frac{Ucos40}{cos70} = V

    try subbing that into the 2nd equation?

    NB cos 20 = sin 70
    Offline

    0
    ReputationRep:
    (Original post by GHOSH-5)
     Ucos40 = Vcos70
     Ucos50 + Vcos20 = 5
    its just a matter of simultaneous equations....

    look at the top equation:
     \frac{Ucos40}{cos70} = V

    try subbing that into the 2nd equation?

    NB cos 20 = sin 70

    Yeah, though it's probably easier to work out that fraction and sub in the decimal. Subbing that exact fraction in would drive me insane. :p:
    • Thread Starter
    Offline

    0
    ReputationRep:
    wer did u get 50 and 20 from?
    Offline

    12
    ReputationRep:
    (Original post by Elimelim)
    wer did u get 50 and 20 from?
    90-40 = 50, which is the angle between U and the y-axis yeh? same with 20 and V
    • Thread Starter
    Offline

    0
    ReputationRep:
    thank you very much, so u just have to get it to the y axis so it equals 5
    Offline

    12
    ReputationRep:
    (Original post by Elimelim)
    thank you very much, so u just have to get it to the y axis so it equals 5
    as said in question c).... just resolving parallel to the y-axis...
    • Thread Starter
    Offline

    0
    ReputationRep:
    umm on the book it says

    u = 1.82 and v = 4.08

    i didnt get v when doing your formula
    Offline

    12
    ReputationRep:
    did you get U? did you type it into the calculator correctly...
    • Thread Starter
    Offline

    0
    ReputationRep:
    how becuase i cant find u without v

    so if v is wrong

    cos 40/70 doesnt get me 4.08
    Offline

    12
    ReputationRep:
    (Original post by Elimelim)
    how becuase i cant find u without v

    so if v is wrong

    cos 40/70 doesnt get me 4.08
    hang on. have you found U?
    • Thread Starter
    Offline

    0
    ReputationRep:


    i cant find u first becuase you said i have to find v then substitute to find u?
    Offline

    12
    ReputationRep:
    no. i said substitute:

    V=\frac{Ucos40}{cos70}

    into the second equation. like this:

    Ucos50 + (\frac{Ucos40}{cos70} \times cos20) = 5
    • Thread Starter
    Offline

    0
    ReputationRep:
    Im very very confused now
    Offline

    12
    ReputationRep:
    (Original post by Elimelim)
    Im very very confused now
    ok i rearranged the first equation to make V the subject. i substituted that for V into the 2nd equation. we can solve it like this:

     Ucos50 + (\frac{Ucos40}{cos70} \times cos20) = 5

     U(cos 50+ \frac{cos40 \times cos 20}{cos70}) = 5

    and then divide by the big bracket on the left to get U, then shove that all in a calculator. find U. and then sub back the value of U into equation 1 to get V. see?
    • Thread Starter
    Offline

    0
    ReputationRep:
    but i dont get any of them answers ;s

    but i dont get u as 1.82.

    i get when you substiute v into the equation but after that im lost
    Offline

    12
    ReputationRep:
    hmm i get the answers in the book. is your calculator in radians?
    • Thread Starter
    Offline

    0
    ReputationRep:
    so first of all you times out that bracket you posted and you should get 1.82 for u?

    then u put 1.82 into the question to get v?
    Offline

    12
    ReputationRep:
    (Original post by Elimelim)
    so first of all you times out that bracket you posted and you should get 1.82 for u?

    then u put 1.82 into the question to get v?
    the order i shoved it in the calculator:

    cos40 x cos 20 =
    Ans / cos 70 =
    Ans + cos 50 =
    5 / Ans = 1.82.. = U
    Ans x cos 40 =
    Ans / cos 70 = 4.08... = V
    • Thread Starter
    Offline

    0
    ReputationRep:
    forgot to divide by 5 lol thanks

    that is some coplicated thing compared to b4
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: November 15, 2008

University open days

  • University of Exeter
    Undergraduate Open Days - Exeter Campus Undergraduate
    Wed, 24 Oct '18
  • University of Bradford
    Faculty of Health Studies Postgraduate
    Wed, 24 Oct '18
  • Northumbria University
    All faculties Undergraduate
    Wed, 24 Oct '18
Poll
Do protests make a difference in political decisions?
Useful resources

Make your revision easier

Maths

Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

Equations

How to use LaTex

Writing equations the easy way

Equations

Best calculators for A level Maths

Tips on which model to get

Student revising

Study habits of A* students

Top tips from students who have already aced their exams

Study Planner

Create your own Study Planner

Never miss a deadline again

Polling station sign

Thinking about a maths degree?

Chat with other maths applicants

Can you help? Study help unanswered threads

Groups associated with this forum:

View associated groups

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.