Angle 2=3, so angle 1=4 because angles ABC & BCD equal 90°. When you add together the angles of a triangle you get 180 and if you could put angle 1 and 4 together it would look like an upward version.
That is the best way I could describe it. Hope that helps.
60cm2 !! enjoy your day !!
-21x+31 this is the answer you were looking for
So here, ABCD is being inscribed in a circle, so ABCD is a cyclic quadrilateral (as inscribed in a circle) also, there exists a property of cyclic quadrilateral, i.e, the sum of opposite angles of a cyclic quadrilateral is 180°, so we can just write the following equation using this :



