Answer:-
Given: m∠QRS=76°
Prove: △PQR is an obtuse triangle.
Proof:- ∠ORS=76° [given]
∠PRQ and ∠QRS are supplementary . [Linear pair postulate.]
m∠PRQ+76°=180° [Substitution property of equality]
m∠PRQ=104° [Subtraction property of equality]
∠PRQ is an obtuse angle [Definition of obtuse angle]
ΔPQR is an obtuse triangle.[Definition of obtuse triangle]
