?1?sin2B?1?sin2C?sin2A??sinAsinB,
?sin2C?sin2B?sin2A??sinAsinB,?a2?b2?c2?ab,
????1???5?cosC?,?C?,?B??????.
233412(2)根据正弦定理
ab, ?sinAsinB得b?asinB5?6?2????, ?2sin?2sin????sinA12642??1136?23?3?sinC?ab???2??. 22224?S?ABC?22.(Ⅰ)依题意可得:Sn?1?Sn?又a1?1,?数列?(Ⅱ)令bn?an?1n?11a?an,?an?1??an,?n?1??n. 3n3nn?13n1?an?是首项为1,公比的等比数列. q??n3??ban1a,?n?1?.又b1?1?1,
bn3n11?数列?bn?是以1为首项,为公比的等比数列.
3?1??bn?b1????3?n?1?1?????3?n?1?1?.?an?n????3?2n?1(n?N*).
n?2?1??1??1?Sn?1????2????3?????3??3??3?1?1??1??1???Sn?1????2????3????3?3??3??3??两式相减得:
12301?1???n?1?????3??1??n????3?n?1,
n?1???n?1?????3?n?1?1??n???.
?3?2?1??1??1???Sn?1??????????3?3??3??3?n?1123?1?????3?n?1?1??n???.
?3?nnn1?1?1????n21333????Sn????n?????132?3?1?3
9?93n??1??3??1?.?S???????. ?nn????423?????42??3?
高一下学期期末数学试卷
一、选择题:本大题共12小题,每小题3分,共36分。把答案填在答题卡上。 1.sin600o
的值是( )
A.
1332; B.2; C.?2 D.?12 2.与直线x?3y?1?0垂直的直线的倾斜角为 ( ) A.? B. ? C. 2?
D.5?
63363.△ABC中, a = 1, b =3,A=30°,则B等于 ( )
A.60° B.60°或120°
C.30°或150° D.120°
4.如果等差数列?an?中,a3?a4?a5?12,那么a1?a2???a7? ( ) A.14 B.21 C.28 D.35 5、若a,b,c?R,且a?b,则下列不等式一定成立的是 ( )
A.a?c?b?c B.ac?bc
.c2Ca?b?0 D.(a?b)c2?0
6.设z=x?y, 式中变量x和y满足条件??x?y?3?0?2y?0, 则z的最小值为 ( )
?x A.1 B.?1 C.3
D.?3
7.若M(x,y)在直线上x?2y?1?0移动,则2x?4y的最小值是 ( )
A.22 B.2 C.22 D.42
8、为了得到函数y?2sin(x??36),x?R的图像,只需把函数y?2sinx,x?R的图像上所有的点 ( )
A.向左平移?16个单位长度,再把所得各点的横坐标缩短到原来的3倍(纵坐标不变) B.向左平移?12个单位长度,再把所得各点的横坐标缩短到原来的3倍(纵坐标不变)
C.向左平移