cos^2 （7π/12）-sin^2 （7π/12）=

cos^2 （7π/12）-sin^2 （7π/12）
=cos2(7π/12)
=cos(7π/6)
=-cos(π/6)
=-Root 3 / 2

Given sin α = 1 / 7, cos (α + β) = - 11 / 14, and α, β ∈ (0, π / 2), the value of cos β is obtained

∵ α, β ∈ (0, π / 2), ∵ α + β ∈ (0, π), cos (α + β) = - 11 / 14, ∵ sin (α + β) = {1 - (- 11 / 14) ^ 2} = (5 / 14) √ 3. ∵ sin α = 1 / 7, α∈ (0, π / 2), ∵ cos α = {1 - (1 / 7) ^ 2} = (1 / 7) √ 6. ∵ cos β = cos

RELATED INFORMATIONS

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