Proof of a quadrilateral being cyclicWatch
I feel like I'm missing something very obvious here, does anyone have any ideas as to how to do this?
You've found ACB to be x,correct? The sum of angles in a triangle would be 180 degrees. Try moving from there,regardless of whether or not you get an expression as angle ABC.
Ok. BAC and ACB both equal x. Sum of angles in a triangle is 180 degrees. Therefore, ABC would be 180-(x+x), or 180-2x. Now, the proof of a quadrilateral being cyclic is that two opposite angles are supplementary,meaning their sum is 180 degrees. Add ABC to ADC,and you should get the answer. Sorry if I was a bit vague.