Jawabanmu

2014-06-10T22:07:24+07:00
16² = 20² - (15 - r )²    (pakai pytagoras )
( 15 - r ) = 12 cm
r = 3 cm 

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2014-06-10T22:09:48+07:00
(R-r) = √ p² - l²
(15-r) = √ 20² - 16²
(15-r) = √ 400 - 256
(15-r) = √144
(15-r) = 12
r = 15 - 12
r = 3cm
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