(√3tan48-1)/(2sec48)-cos48
=(√3sin48-cos48)/2-cos48
=√3/2 *sin48-3/2 *cos48
=√3(1/2 *sin48-√3/2 *cos48)
=√3(cos60sin48-sin60cos48)
=√3sin(48-60)
=-√3sin12