B.20. sinα cosβ - sinα cosβ + 2cosα sin β = sinα cosβ +sin β cosα = sin(α+β) = 0.17
.B12 cos(3π\2 - β) = sin β= 0.11; B.13 sin (180-β)= sin β = -0.24
B24 -cos2α+sin2α* ctgα = -cos 2α+ 2sinαcosα* sinα\cosα= -cos2α+2sin²α= -1+2sin²α+2sin²α=4sin²α-1
B25 (sin²α-cos²α)(sin²α+cos²α)\ (cos²α-sin²α)- 1 = -1-1=-2
B23 -(cosαsinα-sinαcosα) \ (sinαcosα+cosαsinα) * 2√3 = - cos(α+β) \ sin(α+β) * 2√3 =
- ctg(α+β) * 2√3 = -ctg 120 * 2√3 = -ctg(180-60) * 2√3 = + ctg60 * 2√3 = 1\√3 * 2√3 = 2