# Math Help - trig equation

1. ## trig equation

Hi I am not sure what substitution to use for this, have tried $cos(x+x)=cosxcosx-sinxsinx$ and then I tried $cos\theta+cosy=2cos(\frac{x+y}{2})cos(\frac{x-y}{2})$

the question is: find all solutions if $2cos2x+4sinxcosx=\sqrt{2}$ in the range $o \leq x \leq 2\pi$

2. Originally Posted by oxrigby
Hi I am not sure what substitution to use for this, have tried $cos(\theta+\theta)=cos\thetacos\theta-sin\thetasin\theta$ and then I tried $cos\theta+cosy=2cos(\frac{x+y}{2})cos(\frac{x-y}{2})$

the question is: find all solutions if $2cos2x+4sinxcosx=\sqrt{2}$ in the range $\leg\theta\leq2\pi$
$2\cos(2x)+4\sin(x)\cos(x)=\sqrt{2}\Rightarrow{\cos (2x)+\sin(2x)=\frac{\sqrt{2}}{2}}$

Does that help?

3. My original post is latex sorted now,,,

4. ok