(cos24+cos(48)-(cos84+cos12)=2cos36cos12-2cos48cos36=
=2cos26*(cos12-cos48)=2cos36*2sin30sin18=4*1/2cos36sin18=
=2cos36sin18
Находим периметр:
длина 130, ширина 130-80=50
(130+50)*2=360
1) 4/115*5= 4*5/115=20/115=4/23
2) 5/14*2/15= 5*2/14*15= 10/210= 1/21
Так как sin^2 (127)=sin^2 (90+37)=cos^2 37
И. sin^2 37+cos^2 37=1, то
12/(sin^2 37+sin^2 127)=
12/(sin^2 37+cos^2 37)=
12/1=12