Turn on thread page Beta
    • Thread Starter
    Offline

    2
    ReputationRep:
    I don't know why I keep getting these wrong, answers at the bottom, thanks

    1) 3sin²θ + sinθ = 0
    (answer is 0, 180, 199, 341, 360)

    2) tan²θ - 2tanθ - 10 = 0
    (answer is 77.0, 113, 257, 293)

    3) sin²θ - 2sinθ - 1 = 0
    (answer 204,336)

    4) tan²2θ = 3
    (answer 30,60,120,150,210,240,300,330)

    5) 4sinθ = tan θ

    (answer 0, 75.5, 180, 284, 360)

    thanks
    Offline

    2
    ReputationRep:
    5) 4sinθ = tanθ
    4sinθ = sinθ/cosθ
    4sinθcosθ - sinθ = 0
    sinθ(4cosθ-1) = 0

    sinθ = 0 or cosθ = 1/4

    θ = 0, 180, 360 or θ = 75.5 , 284.5
    • Thread Starter
    Offline

    2
    ReputationRep:
    you have an excess amount of brain, let me cream some off you, einstein :eek:

    cheers
    Offline

    2
    ReputationRep:
    4) tan²2θ = 3
    tan2θ = ±√3

    2θ = 60, 240 , 420 , 600 or 2θ = -60 , 120 , 300 , 480 , 660

    So, θ = 30 , 60 , 120 , 150 , 210 , 240 , 300 , 330
    • Thread Starter
    Offline

    2
    ReputationRep:
    (Original post by mockel)
    5) 4sinθ = tanθ
    4sinθ = sinθ/cosθ
    4sinθcosθ - sinθ = 0
    sinθ(4cosθ-1) = 0

    sinθ = 0 or cosθ = 1/4

    θ = 0, 180, 360 or θ = 75.5 , 284.5
    i dont get the -sinθ bit, where did that come from?

    edit: nevermind, got it now.
    Offline

    2
    ReputationRep:
    3) sin²θ - 2sinθ - 1 = 0

    Using the quadratic formula:

    sinθ = [2 ± √(4+4)] / 2

    sinθ = (2 ± 2√2)/2

    sinθ = 1±√2

    sinθ cannot be greater than 1, hence

    sinθ = 1-√2

    θ = -24.5 , 204.5 , 335.5

    Therefore, θ = 204.5 , 335.5
    Offline

    2
    ReputationRep:
    2) tan²θ - 2tanθ - 10 = 0

    Using the quadratic formula:

    tanθ = [2 ± √(4+40)] / 2

    tanθ = (2 ± 2√11)/2

    tanθ = 1±√11

    θ = 77.0 , 257.0 or tanθ = -66.7 , 113.3 , 293.3

    So, θ = 77.0 , 113.3 , 257.0 , 293.3
    Offline

    2
    ReputationRep:
    1) 3sin²θ + sinθ = 0
    sinθ(3sinθ+1) = 0

    sinθ = 0 or sinθ = -1/3

    θ = 0 , 180 , 360 or θ = -19.5 , 199.5 , 340.5

    So, θ = 0 , 180 , 199.5 , 340.5 , 360
    • Thread Starter
    Offline

    2
    ReputationRep:
    could you be any smarter:cool:
 
 
 
Turn on thread page Beta
Updated: June 18, 2005
The home of Results and Clearing

4,258

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
A-level students - how do you feel about your results?
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.