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panjang CD - Lebar CE
=12-4=8

[tex] \frac{3}{2 + \sqrt{3} } \times \frac{2 - \sqrt{3} }{2 - \sqrt{3} } = \frac{6 - \sqrt{3} }{4 - 3 } = \frac{6 + \sqrt{3} }{1} = 6 + \sqrt{3} [/tex]
EF = ((AB.CE) + (CD. AE)) ÷ AC
= ((7.4) + (12.6)) ÷ 10
= (28 + 72) ÷ 10
= 100 ÷ 10 = C. 10 cm