diketahui segitiga PQR sama kaki,PQ=PR dan besar

Δ Sama Kaki = 2 Sudut Sama Besar
∠Δ = 180°

PQ = PR
∠QPR = 30°

Maka
x + x + 30 = 180
2x = 180 - 30
2x = 150
x = 150 ÷ 2
x = 75°

∠Q = 75°
∠R = 75°