In ∆PRT,
∠PTR + ∠PRT + ∠RPT = 180°
| ∵ The sum of all the angles of a triangle is 180°
⇒ ∠PTR + 40°+ 95° = 180°
⇒    ∠PTR + 135° = 180°
∠   ∠PTR = 45°
⇒    ∠QTS = ∠PTR = 45°
| Vertically Opposite Angles
In ∆TSQ,
∠QTS + ∠TSQ + ∠SQT = 180°
| ⇒ The sum of all the angles of a triangle is 180°
⇒ 45° + 75° + ∠SQT = 180°
⇒ 120° + ∠SQT = 180°
⇒    ∠SQT = 180° - 120° = 60°.
The side EF, FD and DE of a triangle DEF are produced in order forming three exterior angles DFP, EDQ and FER respectively. Prove that
∠DFP + ∠EDQ + ∠FER = 360°.
OR
Prove that the sum of the exterior angles of a triangl is 360°.Â