4/9 = 0,4(4), 2/11 = 0,18(18), 4/27 = 0,148(148), 14/45 = 0,31(1)
1) а=455, b=91, a:b=5
2) a=5863, b=451, a:b=13
3) a=399, b=133, a:b=3
4) a=164, b=82, a:b=2
5) a=261, b=87, a:b=3
6) a=814, b=74, a:b=11
2sin40*sin50=2sin40*sin(90-40)=2sin40*cos40=sin(2*40)=sin80
или
2sin40*sin50=2sin(90-50)*sin50=2cos50*sin50=sin(2*50)=sin100
A- 3,7/15=4,11/20
a=4,11/20+3,7/15
a= 4,33/60+3,28/60
a=7,61/60
a=6,31/60
ответ:a=6,31/60