Question

以O为圆心的同心圆大圆的半径OC、OD分别交小圆于A.B,弧AB长为8π,弧CD长为12π,AC=12.则小圆半径为

Answer 1

角COD=角AOB;

CD/AB=R/r=12/8=3/2;

OA/OC=2/3; AC=12cm,小圆半径=OA=24cm,大圆半径R=OC=36cm

弧AB的长为8πcm=角AOB/360 * 2πr

角AOB/360 =4/r=4/24=1/6;

角COD==360/6=60;