tolong jawab pertanyaan ya

Matematika, 27 Februari 2018
Geometri

46. 
sudut DAC = BEC,  ADC = EBC, dan DCA = ECB
segitiga ABC kongruen dengan EBC

panjang AD = EB
EC = CD + DE
      = 8 + 9 
      = 17
BC = 8
[tex]EB^{2} \\ = EC^{2} - BC^{2} \\ = 17^{2} - 8^{2} \\ = 289 - 64 \\ = 225 [/tex]
EB = 15
AD = EB = 15m

47.
panjang karton = 30 + 5 + 5 = 40
[tex] \frac{lebar}{40} = \frac{36}{30} = \frac{6}{5} [/tex]
5 lebar = 6 x 40
            = 240
lebar = 240 : 5 = 48 

karton 
= p x l
= 40 x 48
= 1920

foto
= p x l
= 30 x 36
= 1080

selisih
= 1920 - 1080
= 840 cm2