luas segitiga by clickmath4u

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									LUAS SEGITIGA
                                      C

      7 cm                  75o
                                          4 cm
                 L ??
  A                                        B



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                Luas segitiga                          = 1/2 alas x tinggi
        B

                                            sin C = h/a


    c                   a
                                                     h = a sin C
        h

                                                     Luas = 1/2 b x a sin C

A                                                C
            b                                        Luas = 1/2 ab sin C


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                  C


      b                        a



  A                                       B
                  c


Luas = 1/2 ab sin C
Luas = 1/2 ac sin B
Luas = 1/2 bc sin A
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               Contoh
                                                C

               7 cm                   75o
                                                    4 cm
                           L ??
         A                                           B


Luas = 1/2 ab sin C
     = 1/2 x 4 x 7 sin 75
     = 14 x 0.966 = 13.5 cm2
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                                                            C

Contoh (lagi)                                     b
                                                                4 cm

                                       30o                80o
                       A                              c          B

  a   =     b                       4    =   b
sin A     sin B                   sin 30   sin 80
  b = 4 x sin 80 = 7.88 cm
        sin 30
C = 180 - A - B = 180 - 30 - 80 = 70o
Luas = 1/2 ab sin C
     = 1/2 x 4 x 7.88 x sin 70 = 14.8 cm
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