Turn on thread page Beta
    • Thread Starter
    Offline

    12
    ReputationRep:
    6 (a) (i) Given that tan 2x + tan x = 0 , show that tan x = 0
    or tan^2x =3 .

    ^that is the question, it is from the aqa jan 2011 paper.

    I have got to 2tanx + tanx(1-tan^2x) / 1 - tan^2x = 0 but i do not know what to do next?

    I went on the worked solutions and they have gotten to the same point as me and then have got tanx(2+1-tan^2x) = 0 i do not know how they have got to this??

    this is the worked solutions link question 6 (a) (i) : http://www.mrbartonmaths.com/resourc...0Solutions.pdf
    • Community Assistant
    Offline

    20
    ReputationRep:
    Community Assistant
    (Original post by Jack210)
    6 (a) (i) Given that tan 2x + tan x = 0 , show that tan x = 0
    or tan^2x =3 .

    ^that is the question, it is from the aqa jan 2011 paper.

    I have got to 2tanx + tanx(1-tan^2x) / 1 - tan^2x = 0 but i do not know what to do next?

    I went on the worked solutions and they have gotten to the same point as me and then have got tanx(2+1-tan^2x) = 0 i do not know how they have got to this??

    this is the worked solutions link question 6 (a) (i) : http://www.mrbartonmaths.com/resourc...0Solutions.pdf
    Just multiply through by 1-\tan^2 x then factor out \tan x
    • Thread Starter
    Offline

    12
    ReputationRep:
    (Original post by RDKGames)
    Just multiply through by 1-\tan^2 x then factor out \tan x
    i've tried doing that, i think i'm going wrong somewhere :/ could you show me step by step how you do it please?
    • Community Assistant
    Offline

    20
    ReputationRep:
    Community Assistant
    (Original post by Jack210)
    i've tried doing that, i think i'm going wrong somewhere :/ could you show me step by step how you do it please?
    Not much room to go wrong tbh...


    \dfrac{2\tan x + \tan x(1-\tan^2 x) }{1- \tan^2 x } = 0

    \Rightarrow 2\tan x + \tan x (1-\tan^2 x ) = 0

    \Rightarrow \tan x(2+1-\tan^2 x ) = 0
    Offline

    19
    ReputationRep:
    (Original post by Jack210)
    6 (a) (i) Given that tan 2x + tan x = 0 , show that tan x = 0
    or tan^2x =3 .

    ^that is the question, it is from the aqa jan 2011 paper.

    I have got to 2tanx + tanx(1-tan^2x) / 1 - tan^2x = 0 but i do not know what to do next?

    I went on the worked solutions and they have gotten to the same point as me and then have got tanx(2+1-tan^2x) = 0 i do not know how they have got to this??

    this is the worked solutions link question 6 (a) (i) : http://www.mrbartonmaths.com/resourc...0Solutions.pdf
    Listen baby thats so easy.
    Use the double angle formula to turn tan2x into the double angle identity. then times by the denominator what ever it is then FACTORISE
    Offline

    19
    ReputationRep:
    (Original post by RDKGames)
    Not much room to go wrong tbh...


    \dfrac{2\tan x + \tan x(1-\tan^2 x) }{1- \tan^2 x } = 0

    \Rightarrow 2\tan x + \tan x (1-\tan^2 x ) = 0

    \Rightarrow \tan x(2+1-\tan^2 x ) = 0
    Yes G that is correct, I did my C4 mock its favjing basic innit?
    • Thread Starter
    Offline

    12
    ReputationRep:
    (Original post by RDKGames)
    Not much room to go wrong tbh...


    \dfrac{2\tan x + \tan x(1-\tan^2 x) }{1- \tan^2 x } = 0

    \Rightarrow 2\tan x + \tan x (1-\tan^2 x ) = 0

    \Rightarrow \tan x(2+1-\tan^2 x ) = 0
    i am so confused because i don't understand where the denominator has gone? if you multiply by 1-tan^2x wouldn't the numerators numbers be multiplied by it? and also i don't get how 2tanx+tanx(1-tan^2x) has got to tanx(2+1-tan^2x)
    • Community Assistant
    Offline

    20
    ReputationRep:
    Community Assistant
    (Original post by Jack210)
    i am so confused because i don't understand where the denominator has gone? if you multiply by 1-tan^2x wouldn't the numerators numbers be multiplied by it? and also i don't get how 2tanx+tanx(1-tan^2x) has got to tanx92+1-tan^2x)
    The 1-\tan^2 x is the denominator, multiplying both sides of the equation by it cancels it out.
    Then just factor out \tan x, mate.

    These shouldn't be issues at C4.
    Offline

    15
    ReputationRep:
    (Original post by Jack210)
    i am so confused because i don't understand where the denominator has gone? if you multiply by 1-tan^2x wouldn't the numerators numbers be multiplied by it? and also i don't get how 2tanx+tanx(1-tan^2x) has got to tanx(2+1-tan^2x)
    You're multiplying the left hand side and the right hand side by the same thing, not the numerator and the denominator.
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: March 8, 2018

2,790

students online now

800,000+

Exam discussions

Find your exam discussion here

Poll
Should predicted grades be removed from the uni application process
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

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.