pada gambar di atas, besar BAD=50° dan ABD=70°. Jika DBC = 5x – 3° dan BCD= 3x – 1. tentukan besar ABC​

Jawab:

ΔABD = 180° maka

∠ADB = 180° – ∠DBA – ∠DAB = 180 – 50 – 70 = 60°

∠ADC = 180° maka ∠BDC = 180° – ∠ADB = 180° – 60° = 120°

∠BCD + ∠BDC + ∠DBC = 180°

120° + 5x -3° + 3x – 1° = 180

5x + 3x = 180 – 120° – 3° – 1°

8x = 56 ⇒ x = 7

∠DCB = 3x – 1° = 3(7) – 1 = 21 -1 = 20°

180° ∠DCB – ∠DAB = ∠ABC

180° – 20° – 50° = 110°

pilih menjadi jawaban terbaik kalau benar ya ^-^