Provide missing steps of the equation in the box

CASE 2: B = Ho Idi xi B =! Ho Idl 4 TT 72 dB = dl (x+ a? di' dB, = dB cos 0 = dl a ( x2 + a? ) (x2 + a2 ) 1/ 2 a dBy dB X dB. = dB sin 0 = dl X NA P X 4 7 (x2 + a? ) (x2 + a2 1/2 - 8 dB x