Question

Diagonals AC and BD of parallelogram ABCD intersect at O. If angleBOC = 90° and angle BDC = 50°, find angleOAB

Answer 1

angle BOA = 180-90=90°
angle ABO= BDC=50°(alternate angle )
angle OAB =180-(90+50)
OAB=180-140=40°
May this helped you.