Question

A david's field ABCD,diagonals meet at O. if angle BOC=40° and ange OBA=30°, find angle OAD

Answer 1

A David field is a cubical structure whose each face is a square.
consider square ABCD.See the figure in attachment

In square ABCD,diagonals meet at O.
Boc=40,soaob=140   (supplementary angles)
in ΔAOB,
BAO+AOB+OBA=180
HENCE
BAO=10
NOW
MAO+OAD=90(ANGLE OF A SQUARE)
HENCE,
OAD=80