T-Саша
х-папа
у-Миша
х+у=42
x=42-y
t+х=40
t+42-y=40
t-y= -2
t= y-2
х+у+t=50
42-y+y+y-2=50
y=50-42+2
y=10
x=42-y
x=42-10
x=32
t=y-2
t=10-2
t=8
Ответ:Саше 8 лет, папе 32, Мише 10
1) S = a² = 7² = 49 см²;
2) Р = 2 (a + b) = 2 ( 7 + 10) = 2 * 17 = 34 см;
S = a * b = 7 * 10 = 70 см²;
3) P = 2 (a + 3a) = 2 (7 + 3 * 7) = 2 (7 + 21) = 2 * 28 = 56 см;
4) P = 2 (a + a + b) = 2 (7 + 7 + 10) = 2 * 24 = 48 см.
Sin(x/4-3)≤√2/2
Пусть x/4-3=t, тогда sint≤√2/2 или
-5π/4+2πn≤t≤π/4+2πn,
-5π/4+2πn≤ x/4-3 ≤π/4+2πn,
-5π/4+3+2πn≤x/4≤π/4+3+2πn
-5π+12+8πn≤x≤π+12+8πn,n∈Z