sinA^2/sinB^2+cosA^2*cosC^2=1,求证tanA^2*cotB^2=sinC^2
问题描述:
sinA^2/sinB^2+cosA^2*cosC^2=1,求证tanA^2*cotB^2=sinC^2
三角比刚刚接触.求详细证明.
好的一定再加
答
sinA^2/sinB^2+cosA^2*cosC^2=1sinA^2+(sinB)^2*(cosA)^2*(cosC)^2=(sinB)^2sinA^2+(sinB)^2*(cosA)^2*(cosC)^2=(sinB)^2*[(cosA)^2+(sinA)^2]=(sinB)^2*(cosA)^2+(sinB)^2*(sinA)^2(sinA)^2-(sinB)^2*(sinA)^2=(s...