Proving algebraic equations with circle theorems 
I got as far as stating that OBP=90˚ (as angle between tangent and radius is always 90˚), and thus CBO=90˚- 2x. CBO=OCB as they are bases in a isosceles. COB=180-90-2x-90-2x. But after this, i am clueless.
I am stuck with this Question. It is from a GCSE Further Maths past paper. Despite seeing online tutorials, and checking the answer scheme, I still don't understand how you solve this question. Could you please show me a step by step explanation of how you solve this question. Thank you.


ANSWER:


I am also doing Further Maths GCSE and what i would do is draw a line from B to D (this is a lot shorter) this would create the alternate segment theorem for angles therefore $BDC$ would be $2x$ and $BDO$ and $DBO = x$ which means $ BOD = 180- 2x$ which means $y = 360 − 90 − 90 − (180 − 2x)$
$y = 2x$
