在△ABC中，a，b，c分别为角A，B，C所对的边．已知角A为锐角，且b=3asinB，则tanA=______．
在△ABC中，角A为锐角，且b=3asinB，由正弦定理可得 sinB=3sinAsinB，∵sinA≠0，
故sinA=
，∴cosA=1 3
=1-sin2A
tanA=2 2 3
=sinA cosA
，2 4
故答案为
．2 4
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| Valentine's Day was the time my father chose to show his love for the special people in his life.Over the years I fondly (天真地) thought__1__him as my "Valentine man"． My first recollection of the__2__he could bring to Valentine's Day came when I was six.That morning at the breakfast table I found a card and a giftwrapped package at my chair.The card was__3__"Love, Dad" and the gift was a ring with a small piece of red glass to__4__my birthstone,a ruby (红宝石)。There is__5__difference between red glass and rubies to a child of six,and I remember__6__that ring with pride that all the cards in the world__7__not surpass (超越)． __8__I grew older,the gifts gave__9__to heartshaped boxes filled with my__10__chocolate and always included a__11__card signed "Love,Dad"．In those years my thankyou became__12__of a perfunctory (敷衍) response.The cards seemed less__13__,and I took for granted that the Valentine would__14__be there.I had__15__my hopes and dreams in receiving cards and gifts from "significant others" and "Love, Dad" just didn't seem quite__16__. His final card remains on my desk today.It's a__17__of how special fathers can be and how important it has been to me over the years to know that I had a father who continued a__18__of love with simple acts of understanding and an ability to express happiness over the people in his life. Those things never__19__,nor does the memory of a man who never__20__being my valentine. | |||
| ( )1. A.of ( )2．A.memory ( )3．A.read ( )4．A.recover ( )5．A.much ( )6．A.having ( )7．A.could ( )8. A.Because ( )9．A.room ( )10．A.favorite ( )11．A.usual ( )12．A.less ( )13．A.important ( )14．A.surely ( )15．A.let ( )16．A.suitable ( )17．A.signal ( )18．A.tradition ( )19．A.lose ( )20．A.thought | B．about B．magic B．written B．resemble B．little B．owning B．did B．Since B．way B．lovely B．common B．little B．beautiful B．always B．kept B．enough B．certificate B．hobby B．die B．wanted | C．up C．puzzle C．shown C．represent C．great C．we aring C．must C．When C．honour C．dear C．strange C．more C．familiar C．regularly C．placed C．effective C．consequence C．habit C．miss C．tried | D．over D．present D．signed D．replace D．less D．watching D．should D．As D．seat D．precious D．special D．much D．standard D．often D．remembered D．sacred D．reminder D．custom D．appear D．stopped |