匿名 "|" 2014-05-20 "|" 分享已知向量a=(2cos(x-派/6),-2sin(x-派/4)),b=(cos(x-派/6),-sin(x+派/4)),f(x)=ab-2(1)..求函数的最小正周期

Question

匿名 "|" 2014-05-20 "|" 分享
已知向量a=(2cos(x-派/6),-2sin(x-派/4)),b=(cos(x-派/6),-sin(x+派/4)),f(x)=ab-2 (1)..求函数的最小正周期

Answer 1

f(x)=向量a.向量b-2.f(x)=2cos(x-π/6)*cos(x-π/6)+(-2sin(x-π/4)*(-sin(x+π/4)-2.=2cos^2(x-π/6)+2sin(x+π/4)*sin(x+π/4)-2.=1+cos(2x-π/3)+2{(-1/2)[cos2x-cos(-π/2)]}-2.=cos(2x-π/3)-cos2x-1.=-2sin(2x...