A simple trigonometrical equation.

[vandana panchal]

If:

$$\cos(2\theta) = \left(\sqrt{2}+1\right)\left(\cos(\theta)-\frac{1}{\sqrt{2}}\right)$$

then what is the value of $\theta$?

 

[MarkFL]

Hello vandana panchal, and welcome to MHB! :D

I wrapped your $\LaTeX$ code in MATH tags, so that it will be parsed correctly. I also made a few minor tweaks to the code.

For future reference, we do ask that our users show what they have tried so we know where you are stuck, and can offer better help.

To get you started, I think I would try a double-angle identity for cosine on the left, and then write the resulting quadratic in $\cos(\theta)$ in standard form, and apply the quadratic formula. What do you find?