1+(tanB)^2=(secB)^2=1/(cosB)^2所以(cosB)^2=5/4 (sinB)^2=4/5同理:(sinC)^2=9/10 三角形ABC的最短边是角C所对的边然后用正弦定理...sinA=√2/2 a=√5....答案=6√5/2
