Sin30ctg30-cos30
cos^2Ltg^2L+sin^2Lctg^2L
1+sin(П+2)cos(3П/2+L)
(1-sin30)*(1+sin30)+(1+cos30)(1-cos30)

1). $sin 30^{circ}*ctg 30^{circ} - cos 30^{circ} = sin 30^{circ}* frac{cos 30^{circ}}{sin 30^{circ}} - cos 30^{circ} =$
$=cos 30^{circ} - cos 30^{circ} = 0$

2). $cos^{2} alpha *tg^{2} alpha +sin^{2} alpha *ctg^{2} alpha =sin^{2} alpha +cos^{2} alpha =1$

3). $1+sin( pi + alpha )*cos(frac{3 pi }{2}+ alpha) =1-sin alpha *sin alpha =cos^{2} alpha$

4). $(1-sin30^{circ})(1+sin30^{circ}) +(1+cos30^{circ})(1-cos30^{circ}) =$
$= 1-sin^{2}30^{circ}+1-cos^{2} 30^{circ} = 2-1=1$