hạ đường cao AH.
$AH : AB = sin 38^o => AH= sin 38^o . 11 \approx 6.77 cm $
$AH : AC= sin 30^o=> AC= 6.77 : sin 30^0 = 13.54 cm$
$BH = AH . tan(90^o -38^o)\approx 8.67 cm$
$HC = AH . tan (90^o - 30^o)\approx 11.73cm$
$=> BC\approx 20.4 cm $
=>Chu vi = $11 + 20.4 + 13.54\approx 44.94 cm$