根据题意可知：cosa=√2/10,cosb=2√5/5∴sina=7√2/10,sinb=√5/5,sin2b=4/5,cos2b=3/5∴sin(a+2b)=sinacos2b+cosasin2b=√2/2又∵sina=7√2/10＞√2/2,sin2b=4/5＞√2/2即a＞π/4,2b＞π/4∴a+2b＞π/2∴a+2b=3π/...