Use the data in the drawing to calculate the [tex]\alpha[/tex] angle
(Sorry, I'm not a native english speaker)

Step-by-step explanation:
Opposite angles in a cyclic quadrilateral
are supplementary. (Sum up to 180°)
Hence alpha + 50° = 180°,
Alpha angle = 130°.
Answer:
Sum of the opposite angles of a cyclic quadrilateral is 180°
[tex] \alpha + 50 = 180 \\ \alpha = 180 - 50 \\ \boxed{\alpha = 130}[/tex]