we know that the sum of the internal angles=(n-2)*180° where n=4 (quadrilateral) the sum of the internal angles=(4-2)*180°------> 360° the sum of the internal angles in a quadrilateral is 360 degrees so 360°=∠1+∠2+∠3+∠4 ∠1=90° ∠2=90° ∠3=122° ∠4=? 360=90+90+122+∠4 360=302+∠4 ∠4=360-302 ∠4=58°
