Tolong dong! #Plz_tolong_yak

1a) luas juring AOB = (α°/360°) x π x r²
                                = (72°/360°) x 3,14 x 18²
                                = 203,5 cm²
   b) panjang busur AB = (α°/360°) x 2 π r
                                     = (72°/360°) x 2 x 3,14 x 18
                                     = 22,6 cm
2) keliling = 2 π r
       22     = 2 x 22/7 x r
             r  = 22/6,3
             r  = 3,5 cm
    panjang busur PQ = (80°/360°) 2 x 3,14 x 3,5
                                  = 4,9 cm
3) panjang busur AB = (120°/360°) 2x 22/7 x r
                           40   = 2,09 r
                              r  = 40/2,09
                              r  = 19 cm
     panjang busur CD = (30°/360°) 2 x 3,14 x 19
                                   = 9,9 cm
4) panjang busur = (50°/360°) x 2 x 3,14 x 18
                            = 15,7 cm
5) panjang busur AB = (120/360) x 2 x 3,14 x r
                          88    = 2,1 x r
                             r    = 88 / 2,1
                             r    = 41,9
     panjang busur CD = (30/360) x 2 x 3,14 x 41,9
                                   =  21,9 cm