а) sin3α+sinα= =2sin2α*cosα
б) cos46°- cos74° = = -2sin2α*sinα
в) cos 11π/12 + cos 3π/4 = =
=2cos(20π/24)*cos(π/12)=2cos(5π/6)*cos(π/12)
а) sin3α+sinα= =2sin2α*cosα
б) cos46°- cos74° = = -2sin2α*sinα
в) cos 11π/12 + cos 3π/4 = =
=2cos(20π/24)*cos(π/12)=2cos(5π/6)*cos(π/12)