Sin (x/2 +pi/6) = - 1
x/2 + pi/6 = - pi/2 + 2pik
x/2 = - pi/6 - pi/2 + 2pik
x/2 = - 2pi/3 + 2pik // * 2
x = - 4pi/3 + 4pik, k ∈ Z
3sin(10)*0.5*(cos(50-70) - cos(50+70)) = 1.5*sin(10)*(cos(20) - cos(120)) = 1.5*sin(10)*cos(20) - 1.5*sin(10)*cos(180 - 60) = 1.5*0.5*(sin(10-20) + sin(10+20)) + 1.5*sin(10)*cos(60) = -0.75*sin(10) + 0.75*sin(30) + 0.75*sin(10) = 0.75*0.5 = (3/4)*(1/2) = 3/8 = 0.375
1
sina=cosb=√(b²-4)/b
cosa=sinb=4/b
tga=ctgb=√(b²-4)/4
ctga=tgb=4/√(b²-4)
2
sina=cosb=13/16
cosa=sinb=3/4
tga=ctgb=13/12
ctga=tgb=12/13
ОДЗ x-4>0 и x+7>0
x>4 x>-7
ОДЗ x>4
(x-4)(x+7)=12
x²+3x-28-12=0
x²+3x-40=0
D=9+160=169
не удовлетворяет ОДЗ
ответ х=5
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