You are Here: Home >< Maths

# Trig question

Announcements Posted on
Why bother with a post grad course - waste of time? 17-10-2016
1. The question is solve the equation 2SinxCos2x + Sin2x = 0, i cant simplify it to a form where i can solve any ideas?
2. Express sin2x in terms of sinx and cosx then factorise the expression. Then use the fact that .
3. (Original post by SunDun111)
The question is solve the equation 2SinxCos2x + Sin2x = 0, i cant simplify it to a form where i can solve any ideas?
As an alternative to using the sum to product identity shown above, you could also use an identity for cos(2x) and then solve the quadratic in cos.
4. (Original post by notnek)
As an alternative to using the sum to product identity shown above, you could also use an identity for cos(2x) and then solve the quadratic in cos.
(Original post by B_9710)
Express sin2x in terms of sinx and cosx then factorise the expression. Then use the fact that .
Yeah i did it by forming a quadratic using 2SinX ( Cos2x + Cosx) = 0 hence forming a quadratic
5. (Original post by SunDun111)
Yeah i did it by forming a quadratic using 2SinX ( Cos2x + Cosx) = 0 hence forming a quadratic
We may or may not be talking about the same thing.

I meant forming a quadratic to solve Cos2x + Cosx = 0.

So are you okay now or still stuck?
6. (Original post by notnek)
We may or may not be talking about the same thing.

I meant forming a quadratic to solve Cos2x + Cosx = 0.

So are you okay now or still stuck?
Same thing i got it right according to the answer book

the Q was 2SinxCos2x + Sin2x

Rewriting Sin2x as 2SinxCosx

Then factorising 2sinxCos2x + 2 SinxCosx as 2sinx (Cos 2x + cos x) then using an identity for cos2x to find a trig equation to solve.

## Register

Thanks for posting! You just need to create an account in order to submit the post
1. this can't be left blank
2. this can't be left blank
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
1. Oops, you need to agree to our Ts&Cs to register

Updated: June 2, 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.

This forum is supported by:
Today on TSR

### A level maths

Which modules should I take?

Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read here first

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams