1、南充高中 20192020 学年度下期高 2019 级中期考试（文科）数学试卷答案.1211.106.51ADDCBDACCBDB23.161.155.1431.13nn 分分10.41,4,5,1,3,1.25.2,036,.1.17bababxxxbaba 分知由分分由题意知：12.322241.28.,224.242810282.1.182111nnnnSnadadadann 分联解得：又即得：代入中，由余弦定理得在分，由于，即故其中可等价转化为，中，由正弦定理得在12.624,343sin21,312,-123,32,cos2:.26.3,0,3tansincos3.0sin,0,si
2、nsincossin3:sincos3sinsinsin:.1.19222222cbbcbcAbcSbccbbccbAaAbccbaABCAAAAABBBAABBaAbCcBbAaABCABC 分作差得：知由分，舍或即结合题意得：公比为设等比数列12.221221221212222222-2222222212222212,21.26.23-214122142,0.1.2011113213213221213211nnnnnnnnnnnnnnnnnnnnnnTnnnnTnTnTnbaaqqqqaaaaaqqa 分结合题意知分，的单调递减区间为：即令分12.10334215323546sin6cos
3、6cos6sin66sinsin.546sin,32,66,2,0.536cos,566cos232,2cos2.26.23423,23423,2236223.6sin2cossin312cos22cos2sin32.1.212 gxxgZkkkxfyZkkxkZkkxkxxxxxxxf 分的范围是由正弦定理：中同理，在由正弦定理：中在分的面积，即由正弦定理：中同理，即由正弦定理：中在则又中，在12.3,2324,3,236sin32,66,32,0,6sin3cos23sin23sin21cos23sin232sinsin2sinsin224,32,32.sin2,sin26sinsin,6sinsin,.sin24,sin26sinsin,6sinsin,.26.38236sin82312cos12sin423127sin2212sin2221Bsin21127sin224sin127sin4,sinsin,12sin2243sin12sin4,sinsin,.3,4,4312,6CB,3B.1.22CEBEBBBBBBBBBBBCBCEBEBCCBCCECCCEAECECAEACEBBEBBBEAEBEBAEABEACACABSABCACABAECACCAEACEABABAEBABBAEABECAECAEBBAEAEACABC
