Find all the principle value for cos inverse of -1/2? Share with your friends Share 0 Devesh Kumar answered this We know that range of the principal value branch of cos-1 is 0, π.Let cos-1-12 = θ⇒cos θ = -12⇒cos θ = - cos π3⇒cos θ = cosπ - π3 = cos2π3⇒θ = 2π3∈ 0, π 1 View Full Answer R S Prasobh Sankar answered this cos-1( -1/2) = π – cos-1(1/2) [ cos-1(-x) = π – cos-1(x) ] = π – π/3 =2 π/3 .Hope that helps. 1
