Question

Помогите пожалуйста) очень надо)))

Answer 1

5.
sin² α= 1-cos² α = 1 - (5/7)² = 24/49
98 cos2α = 98(cos²α - sin²α) = 98 (25/49 - 24/49) =
= 98 (1/49) = 2

6.
cos² α = 1-sin² α = 1 - (0.6)² = 1-0.36 = 0.64
-18 cos2α = -18 (cos²α - sin²α) =
= -18 (0.64 - 0.36) = -18 * 0.28 = -5.04

7.
a) cos(13π/12) = cos(π + π/12) = -cos(π/12)
√48 (-cos(π/12))² - √12 = √12 (2cos² (π/12) - 1)=
= √12 (2cos² (π/12)- cos²(π/12) - sin² (π/12))=
= √12 (cos² (π/12) - sin² (π/12)) =
= √12 cos(π/6) = √12 * (√3/2) = √36 = 6/2 =3
                                                     2

б) = √32 (1 - 2sin² (3π/8))=
    = √32 (sin² (3π/8) + cos² (3π/8) - 2sin² (3π/8))=
    = √32 (cos² (3π/8) - sin² (3π/8)) =
    = √32 cos(3π/4) = √32 cos(π - π/4) =
    = √32 (-cos (π/4)) = - √32 * (√2/2) = -√64 = -8/2 = -4
                                                                 2