Решить , не могу понять : [email protected] = 0, 8 и p2 < @

Sin2α = 2SinαCosα
Cos²α = 1 - Sin²α = 1 - 0,8² = 1 - 0,64 = 0,36
Cosα = -0,6
Sin2α = 2*0,8*(-0,6) = -0,96

х - 4 = 0   

х = 4

ответ: х  = 4                                                                                                                                                                                                                                             

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