mohon dengan cara terimakasih banyak

<B = <C = (180-90)/2 = 45°
<ADB = 180 - (45+30) = 105°

BD/sin 30 = 2/sin 105
BD = 2 sin 30/sin105
BD = 1 : sin 60 cos 45 + cos 60 sin 45
BD = 1 : 1/2 akar 3 * 1/2 akar 2 + 1/2 * 1/2 akar 2
BD = 1 : akar 3/4 + (1+akar2)/2
BD = akar 6 - akar 2 cm