2√3cos300^-√12sin135^

2√3cos300°-√12sin135°=2√3cos300°-√(4.3)sin135°=
=2√3cos300°-2√3sin135°=2√3(cos300°-sin135°=
=2√3(cos(360°-60°)-sin(90°+45°)=2√3(cos60°-sin45°)=
=2√3(1/2 -√2/2)=2√3.1/2-2√3.√2/2=√3-√3√2=√3(1-√2)