Question

prove that in a paralleologram opposite angles are equal

Answer 1

In ABCD,
AB || CD, ABD=BDC (ALTERNATE ANGLES) (i)
AD || BD, DBC=ADB (ALTERNATE ANGLES) (ii)

ADDING (i)&(ii),
ABD+DBC = BDC+ADB
ABC = ADC

SIMILARLY WE CAN ALSO PROVE BAD=BCD