(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Previous part of the question I have solved:

Express cos(2x) in terms of sin(x):

I got this answer:

cos(2x)=1-2sin^{2}(x)

Hence or otherwise solve the equation

cos(x) + 3sin(x/2) = 2

2. Relevant equations

Double angle formulae:

cos(2x)=cos(^{2}x) - sin(^{2}x)

sin(2x)=2sin(x)cos(x)

3. The attempt at a solution

So basically I'm doing revision on trig, and I know I've come across this problem before, where you are presented with a full angle and a half angle, but I have failed to find an example. It's something to do with halving a double angle formula I think but I can't even start it. How do I get rid of the half angle? I know I should show an attempt, but I can't even start it off. Just a refresher on how to remove half angles would be great thanks :)

(Yes i have read the rules but this problem is difficult to put into that format properly)

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Trigonometry - half angles problems

**Physics Forums | Science Articles, Homework Help, Discussion**