a) $M=\cos(90^0-x)+\sin(x+90^0)-\tan(180^0-x).\cot x=\sin x+\sin(180^0-x-90^0)+\tan x.\cot x=$$=\sin x+\sin(90^0-x)+1=\sin x+\cos x +1$
a) $M=\cos(90^0-x)+\sin(x+90^0)-\tan(180^0-x).\cot x=
$$\sin x+\sin(180^0-x-90^0)+\tan x.\cot x=$
$=\sin x+\sin(90^0-x)+1=\sin x+\cos x +1$