1.cos(a-b)+cos(a+b) 2.sinbcos4b+cosbsin4b 3.sin2a/2sina - вопрос №891327112443224282 от Klari1Faer 28.11.2020 16:37

Question

Алгебра: 1.cos(a-b)+cos(a+b) 2.sinbcos4b+cosbsin4b 3.sin2a/2sina 4.sin2a+sin8a/cos2a-cos8a 5.sin(3π/2+a)+cos(π-a) решите

Klari1Faer · Answer

1.cos(a-b)+cos(a+b) = CosαCosβ +SinαSinβ + CosαCosβ -SinαSinβ=
=2CosαCosβ
2.sinbcos4b+cosbsin4b=Sin(β +4β) = Sin5β
3.sin2a/2sina = 2SinαCosα/2Sinα = Cosα
4.sin2a+sin8a/cos2a-cos8a = 2Sin5αCos3α/2Sin5αSin3α = Ctg3α
5.sin(3π/2+a)+cos(π-a) = -Cosα- Cosα = -2Cosα