Given : AD is angle bisector of ∠ A and AE is perpendicular to BC. To find : ∠ EAD = ? In ∆ ABC, ⇒ ∠A+∠B+∠C=180° ⇒ ∠60°+40°=180° ⇒ ∠A=180°−100°=80° ∵ ∠BAD=∠CAD ⇒ ∠CAD=
80
2
=40° Using external angle property, ⇒ ∠ADE=∠CAD+∠C ⇒ ∠ADE=40°+40°=80° ∴ In ∆ EAD, ⇒ ∠EAD+∠ADE+∠DEA=180° ⇒ ∠EAD+80°+90°=180° ⇒ ∠EAD=180°−170°=10°