Lol, didn't see the middle x was slightly shorter than the other ones
Actually it isn't. So it still was ambigious
To answer the question : consider putting all trigonometric functions on one side, put the square root and the constant on the other, and see what you can work out.
Use the trigonometric identity :
Now arrange the equation :
Square both sides :
Rearrange this :
Expand on the left hand side :
Keep going by factorizing :
Finish this up :
And ... MAGIC ! Quadratic equation :
Can you finish now ? It should be fairly easy.