x Turn on thread page Beta
 You are Here: Home >< Maths

# C2 question, help! watch

1. Hi, I need help with a C2 question.

Triangle ABC is such that BC = 5√2 cm, angle ABC = 30 degrees and angle BAC = θ, where sin θ = √5/8.

Work out the length of AC, giving your answer in the form a√b, where a and b are integers.

thank you!
2. Any workings?
3. Sketch it. It's just the sine rule.
4. I can work out an equivalent answer, but I can't keep it in surd form :/
5. Ah, I had this problem last year, if my instincts are correct then use one of the double angle formulae
6. (Original post by BlastOff)
I can work out an equivalent answer, but I can't keep it in surd form :/
7. 5√2 / √5/8 = x/sin30

5√2 x sin 30 / √5/8 = 12.6

The answer to the question is 4√10, which is 12.6
8. 5√2 / √5/8 = x/sin30

But sin30 = 0.5...

So x/sin30 = x/0.5 = 2x

So 5√2 / √5/8 = 2x

Divide through the fraction on the LHS properly and then divide through by 2 to get x as a surd.
9. sine rule...

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.

This forum is supported by:
Updated: May 23, 2011
Today on TSR

### Loughborough better than Cambridge

Loughborough at number one

Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams