Cos2a=cos^2(a)-sin^2(a)
cos^2(a)=1-sin^2(a)=1-(√2-1)^2=1-(2-2√2+1)=-2+2√2
cos2a=-2+2√2-(√2-1)^2=-2+2√2-3+2√2=-5+4√2
7896:56=141
4140:12=345
10944:48=228
2336:32=73
надеюсь правельно
А) 1)-2/5*3/5*4/5=-2*3*4/25*5; 2)19/25-24/25*5=95/125-24/125=71/125; б) -9ц3/5*5/16=-(48*5)/5*16=-3; 2)3,4^2=11,56; 3)-3-11,56+9,06=-14,56+9,06=-(14,56-9,06)=-5,5))))
1)AB/AD=BC/DC
AB/AD=BC/(AC-AD)
10/AD=15/(20-AD)
200-10AD=15AD
25AD=200
AD=8
CD=20-8=12
2)AB/AD=BC/DC
16/8=BC/5
8BC=80
BC=10