tg a(1-sin^2a)=sin a*cos^2a/cos a=sin a*cos a=(sin 2a)/2
1+sin^2a+cos^2a=1+1=2
cos^2a*tg^2a+sin^2a*ctg^2a=sin^2a+cos^2a=1
arcsin(-1)-arccos(sqrt(3)/2)=-pi/2-pi/6=-pi/3
cos(arccos1)=cos 0=1
cos(-600)=cos 600=cos(360+240)=cos 240=cos(180+60)=-cos60=-1/2
cos 105+cos 75=c0s(180-75)+cos 75=-cos75+cos 75=0
sin 137*cos 47-sin 47*cos 137=sin(137-47)=sin90=1
tg a(1-sin^2a)=sin a*cos^2a/cos a=sin a*cos a=(sin 2a)/2
1+sin^2a+cos^2a=1+1=2
cos^2a*tg^2a+sin^2a*ctg^2a=sin^2a+cos^2a=1
arcsin(-1)-arccos(sqrt(3)/2)=-pi/2-pi/6=-pi/3
cos(arccos1)=cos 0=1
cos(-600)=cos 600=cos(360+240)=cos 240=cos(180+60)=-cos60=-1/2
cos 105+cos 75=c0s(180-75)+cos 75=-cos75+cos 75=0
sin 137*cos 47-sin 47*cos 137=sin(137-47)=sin90=1