已知sin(A+π/3)=3/5,A属于(π/6,2π/3),则cosA=?
问题描述:
已知sin(A+π/3)=3/5,A属于(π/6,2π/3),则cosA=?
答
∵A∈(π/6,2π/3) ∴a+π/3∈(π/2,π)∴cos(a+π/3)
已知sin(A+π/3)=3/5,A属于(π/6,2π/3),则cosA=?
∵A∈(π/6,2π/3) ∴a+π/3∈(π/2,π)∴cos(a+π/3)