2Sina * Cos pi/12 * Sin pi/12 = Sina * (2Cos pi/12*Sin pi/12) =
= Sina * Sin pi/6 = Sina * 1/2 = 1/2 Sina
При упрощении была использована формула
2SinaCosa = Sin2a
Sin pi/6 = 1/2
9 х^2 - 16 = 0
9 х^2 = 16
х^2 = 16/9
х = 4/3
Sin Фи = -1
Фи = -π/2 +2πn, n∈Z
Фи∈[0; 4π]
0≤ -π/2+2πn ≤ 4π
π/2 ≤ 2πn ≤ 4π +π/2
π/2 ≤ 2πn ≤ 9π/2
<u> π </u> ≤ n ≤ <u> 9π </u>
2*2π 2*2π
1/4 ≤ n ≤ 9/4
0.25 ≤ n ≤ 2.25
n=1 Фи= -π/2 +2π = 3π/2
n=2 Фи= -π/2 +2π*2 = -π/2 +4π = 7π/2
Ответ: 3π/2; 7π/2.
+ 3n -
=
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<span>если m=12, n= -3, то
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=
=
= -
= -2
(√7+2)(√7-2)=(√7)²-2²=7-4=3