Có góc pOt phụ với góc mOn hay:
góc pOt + góc mOn = 900900
=> góc pOt = 900900- góc mOn
=> góc pOt = 900−360900−360
=> góc pOt = 540540
Có góc nOt + góc pOt + góc mOn = 18001800
=> góc nOt = 18001800- (góc pOt + góc mOt)
=> góc nOt = 1800−9001800−900
=> góc nOt = 900900