jika sudut BFC 30°, sudut BCF 36°, dan sudut BGF 40° tentukan besar sudut FBG

∠BFC = 30°
∠BCF = 36°
∠BGF = 40°
∠FBG = ?
∠BCF = ∠CFG = 36°
∠BFG = ∠CFG + ∠BFC 
           = 36° + 30° = 66°
∠BFG + ∠BGF + ∠FBG = 180°
36° + 40° + ∠FBG = 180°
∠FBG + 66° = 180°
∠FBG  = 180° - 66°
∠FBG  = 74°