82-7*6+19=82+19-7*6
82-7*6+19=82-(7*6-19)
82-(7*6-19)=82+19-7*6
82-7*6-19≠82-(7*6-19)82-(7*6-19)≠82-7*6-19
Ctg(7arcctg(-√3)+25π/4)=Ctg(7(5π/6)+6π+π/4)=Ctg(35π/6+π/4)=
=Ctg(6π-π/6+π/4)=Ctg(-2π/12+3π/12)=Ctg(π/12)=cos(π/12)/sin(π/12)=
=2cos²(π/12)/[2cos(π/12)sin(π/12)]=(1+cos(π/6))/(sin(π/6)=
=(1+√3/2)/(1/2)=2+√3
А)
470мин=7ч48мин
306мин=5ч6мин
615мин=10ч15мин
429мин=7ч9мин
б)
98ч=4сут2час
250ч=10сут10ч
50ч=2сут2ч
100ч=5сут
5/6*4,2х-5/6*11/5у-5,4*2/9х-5,4*1,5у=3 1/2х-у-1 1/5х-8,1у=3 1/2х-1 1
5х-7,1у=2,3х-7,1у