A cyclic quadrilateral has four sides with each corner touching the inside circumference of a circle.
Prove that the opposite angles in a cyclic quadrilateral add up to 180°.
i.e. Angle m + n = 180°
Draw a line from to the centre O from the left and right corner of the shape
Now compare the angles at the centre to the angles at the circumference
Angle r is twice angle m and angle s is twice n. So r+s is twice m+n
s + r = 360° so m+n = 180°
Find the value of x: