Tolong dong jawab pakai cara ya

13) Luas juring COD = (α/360°) π r²
                           80   = (60°/360°) π r²
                           80   = 1/6 π r²
                        π r²    = 80 x 6
                                  = 480

       ∠BOC = 90° - 60° = 30°
       Luas juring BOC   = (30°/360°) π r²
                                     = (30°/360°) 480
                                     = 40 cm
14) sudut berpelurus = 180°
      ∠AOC + ∠BOC    = 180°
                     ∠AOC    = 180° - ∠BOC
                                   = 180° - 40°
                                   = 140°
      karena terletak pada busur yang sama dan titik O adak titik pusat lingkaran maka
      ∠ADC = 1/2 ∠AOC
                 = 1/2 (140°)
                 = 70°
15)  berlaku sifat2 jajaran genjang ACBD
       ∠A = ∠B 
       ∠B = 180 - (2x° + 5x°)
             = 180° - 7x°