Turn on thread page Beta

C2 Radians HELP watch

    • Thread Starter

    Hi all,

    I've been working through this pack,

    I do not understand how one gets to the answer of the first question (7) part b.
    You can see the question on the above link (the first question) but here it is anyway:

    7. In the triangle ABC, AB = 8 cm, AC = 7 cm, ∠ABC = 0.5 radians and ∠ACB = x radians.

    a) Use the sine rule to find the value of sin x, giving your answer to 3 decimal places.

    This is fine,
    sin(0.5) / 7 = sin(x) / 8
    Therefore sin(x) = (sin(0.5)*8) / 7
    = 0.548 (correct)

    Given that there are two possible values of x,
    (b) find these values of x, giving your answers to 2 decimal places

    ^^^??? How ???^^^

    Just like where you answer questions in degrees, you have to take into account all other angles that would leave you with the same answer. This is where you would use a CAST diagram, but instead of doing 180-angle, use Pi-angle.

    To check you can plug this number into the first equation. You already have the first angle from part A.

    Something to note is that your angle MUST be less than pi-0.5 otherwise all the angles in the triangle are squiffy and there are only 2 angles (same as why there are less than 180degrees in triangle)

    Hope this helps!

    CAST diagrams or draw the sinx graph. You'll notice two values where your value of sinx intersects the graph y = sinx.
Submit reply
Turn on thread page Beta
Updated: May 24, 2016

University open days

  • Manchester Metropolitan University
    Postgraduate Open Day Postgraduate
    Wed, 14 Nov '18
  • University of Chester
    Chester campuses Undergraduate
    Wed, 14 Nov '18
  • Anglia Ruskin University
    Ambitious, driven, developing your career & employability? Aspiring in your field, up-skilling after a career break? Then our Postgrad Open Evening is for you. Postgraduate
    Wed, 14 Nov '18
Should Banksy be put in prison?
Useful resources

Make your revision easier


Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here


How to use LaTex

Writing equations the easy way


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