Turn on thread page Beta
    • Thread Starter
    Offline

    1
    ReputationRep:
    Solve in the interval 0< (theta) < 180 degrees

    2cot^2(theta)= 7cosec(theta) - 8

    Confused on how to answer this.

    I made the 2 cot^2 theta 2cos^2(theta)/sin^2(theta) and the 7cosec(theta) 7/sin(theta) but now I don't know what to do many thanks
    Offline

    12
    ReputationRep:
    Multiply through by \sin^{2}\theta and then replace the cos with the equivalent in sin.
    • Thread Starter
    Offline

    1
    ReputationRep:
    I still confused, So I've times by sin^2 (theta) so I've got

    2cos^2(theta)=7sin(theta) - 8 sin^2(theta)

    So then 8sin^2(theta)+2cos^2(theta) = 7sin(theta)

    so 7sin(theta) = 10 which doesnt work? What have I done wrong?
    • Thread Starter
    Offline

    1
    ReputationRep:
    I still confused, So I've times by sin^2 (theta) so I've got

    2cos^2(theta)=7sin(theta) - 8 sin^2(theta)

    So then 8sin^2(theta)+2cos^2(theta) = 7sin(theta)

    so 7sin(theta) = 10 which doesnt work? What have I done wrong?
    Offline

    12
    ReputationRep:
    (Original post by joestevens2092)
    I still confused, So I've times by sin^2 (theta) so I've got

    2cos^2(theta)=7sin(theta) - 8 sin^2(theta)

    So then 8sin^2(theta)+2cos^2(theta) = 7sin(theta)

    so 7sin(theta) = 10 which doesnt work? What have I done wrong?
    Ah, I assume you've tried to use \sin^{2}\theta + \cos^{2}\theta = 1??

    Unfortunately that only works when the coefficients are the same (obviously you'd need to change the constant to match the coefficients).

    Re-write the cos^2 in terms of sin and then solve as you should be left with a quadratic in sin.
    • Thread Starter
    Offline

    1
    ReputationRep:
    got it cheers
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: September 27, 2010
The home of Results and Clearing

1,295

people online now

1,567,000

students helped last year

University open days

  1. Bournemouth University
    Clearing Open Day Undergraduate
    Fri, 17 Aug '18
  2. University of Bolton
    Undergraduate Open Day Undergraduate
    Fri, 17 Aug '18
  3. Bishop Grosseteste University
    All Courses Undergraduate
    Fri, 17 Aug '18
Poll
Will you be tempted to trade up and get out of your firm offer on results day?
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.