Hey there! Sign in to join this conversationNew here? Join for free

C2 trig am i going about this the right way? Watch

    • Thread Starter
    Offline

    0
    ReputationRep:
    I need to find correct to 1dp the two smallest postive values of theta which satisfys sin theta= -0.84

    so first of all i did inverse sin theta -0.84 = -57.1 then using the symmetry property sin(180-theta)=sin theta I did 180-(-57.1)=237.1 for the first then i did 360+57.1 to get 302.9

    Also im ot too sure why for some questions such as the example given you use the supplimentary rule sin(180-theta)=sin theta

    but for others such as cos theta =0.8 we use the oeriodic property cos(theta-360)=cos theta how can you tell what rnage it will be in?
    Offline

    2
    ReputationRep:
    Your answers are correct but you made a slight typo. 302.9 is 360-57.1 not 360+57.1.

    You can always use the rules for sin(180-theta) etc but to determine which rule you want to use, always sketch a graph to help you decide which solutions to find.
    Offline

    0
    ReputationRep:
    use the cast system
    Offline

    1
    ReputationRep:
    Sketching the graph is the best way to start on any of these trig questions!
 
 
 
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • Poll
    Did TEF Bronze Award affect your UCAS choices?
    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
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • 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

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