数学必修五详细知识点

Question

数学必修五详细知识点

Answer 1

等差:an=a1+(n-1)d Sn=a1n+n(n-1)/2*d =n(a1+an)/2
等比:an=a1*q^n Sn=A1(1-q^n)/(1-q) =(a1-a1q^n)/(1-q) =(a1-an*q)/(1-q) =a1/(1-q)-a1/(1-q)*q^n ( 即A-Aq^n) (前提：q≠1)答案补充
正弦定理:a/sinA=b/sinB=c/sinC=2R(外接圆直径)余弦定理:a^2=b^2+c^2-2bc*conA b^2=a^2+c^2-2ac*conB c^2=b^2+c^2-2ab*conC cosA=b^2+c^2-a^2/abc cosB=a^2+c^2-b^2/2ac cosC=a^2+b^2-c^2/2ab
基本不等式:根号下ab≤a+b/2(a≥0,b≥0)如果a,b是正数,那么根号下ab≤a+b/2(当且仅当a=b时取"=")