sin^2c+cos^2c=1cos∠c=1/4sin^2c=15/16 三角形中各角大于0小于180所以sinc>0sinc=√15/4(2)2sinA=sinCsinA=√15/8a=2 a/sinA=c/sinC代入得c=4c^2=a^2+b^2-2abcosc16=4+b^2-2X2X1/4bb^2-b-12=0得b=4...