11.已知ΔABC\Delta ABCΔABC的内角AAA,BBB,CCC所对的边分别是aaa,bbb,ccc,且1+tanCtanA=2ba1+\frac{\tan C}{\tan A}=\frac{\sqrt{2}b}{a}1+tanAtanC=a2b,则角C=C=C=___π4\frac{\pi }{4}4π___.