Verify?

[~Jacqueline~]

In the interval [0,2pi] verify:

Sin2xSinx=Cos2x

so far all I've done is substituted with the double angle formula for sin which is Sin2x=2SinxCosx but I just can't seem to get the right answer so that is will equate to Cosx.

 

[pka]

In the interval [0,2pi] verify:
Sin2xSinx=Cos2x

Without grouping symbols that is hard to read.
I assume you mean \(\displaystyle \sin(2x)\sin(x)=\cos(2x)\).
You can learn to use LaTeX:
[TEX]\sin(2x)\sin(x)=\cos(2x)[/TEX] is the code for that.

Now it is not true. Let \(\displaystyle x=\frac{\pi}{4}\) to see that it is false.

 

[~Jacqueline~]

yes you're right I did mean that, but how would you work it out using the double angle formula?

 

[pka]

yes you're right I did mean that, but how would you work it out using the double angle formula?

If the question is to show that \(\displaystyle \sin(2x)\sin(x)=\cos(2x)\) is an identity, then that is false. It is not an identity.
The word verify suggests you are to work with identities.
If you mean solve the equation do not use verify.

Which is it, solve or verify?