Question

数学必修5重点

Answer 1

正弦定理：a/sinA=b/sinB=c/sinC

余弦定理：a^2=b^2+c^2-2bc*cosA

b^2=a^2+c^2-2ac*cosB

c^2=a^2+b^2-2ab*cosC

延伸（求三角形面积）：

S=1/2bc*sinA

=1/2ac*sinB

=1/2ab*sinC

等差数列：

an=a1+(n-1)d

Sn=n(a1+an)/2

=na1+n(n-1)d/2

等比数列：

an=a1*q^n-1

Sn=a1(1-q^n)/1-q

=a1-anq/1-q