Hey! Sign in to get help with your study questionsNew here? Join for free to post

C2 Radians HELP

Announcements Posted on
Why bother with a post grad? Are they even worth it? Have your say! 26-10-2016
    • 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.
Write a reply…


Submit reply


Thanks for posting! You just need to create an account in order to submit the post
  1. this can't be left blank
    that username has been taken, please choose another Forgotten your password?
  2. this can't be left blank
    this email is already registered. Forgotten your password?
  3. this can't be left blank

    6 characters or longer with both numbers and letters is safer

  4. this can't be left empty
    your full birthday is required
  1. Oops, you need to agree to our Ts&Cs to register
  2. Slide to join now Processing…

Updated: May 24, 2016
TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

Cats: Yay or nay?
Useful resources

Make your revision easier


Maths Forum posting guidelines

Not sure where to post? Read here first


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
Study resources

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

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