Question

三角形ABC中,根号2sinC/2的平方+cosC/2,求角C,若abc乘等比数列求sinA

Answer 1

1)√2sin^2C/2+cosC/2=√2(1-cos^2C/2)+cosC/2=√2即cosC/2-√2cos^2C/2=0cosC/2=0或√2/2C∈(0,π) C/2∈(0,π/2)C/2=π/4 C=π/22)abc成等比数列b^2=acsin^2B=sinAsinC=sin^2(A+C)即sinA=cos^2A=1-sin^2AsinA=(-1+...