12sin44°/sin22°sin68°=12sin(2.22°)/sin22°sin68°=
=12.2sin22°cos22°/sin22°sin68°=24cos22°/sin68°=
=24cos22°/cos22°=24
(sin2α=2sinαcosα , sin (90°-α)=cosα)
69 - (13 - y)² = -y²
69 - (169 - 26y + y²) + y² = 0
69 - 169 + 26y - y² + y² = 0
26y - 100 = 0
26y = 100
y = 100/26
y = 50/13
Ответ: 50/13
31 - t² = -(t - 9)²
31 - t² = -(t² - 18t + 81)
31 - t² = 18t - t² - 81
18t - t² + t² = 31 + 81
18t = 112
t = 112/18
t = 56/9
Ответ: 56/9
2у=6
y=3
х+3=9
х=6
ответ: (6;3)