问题补充:
已知向量a=(根号2,-2),b=(sin(π/4+2x),cos2x)(x属于R).设函数fx=a*b,求f(-π/4)的值那f(x)的最大值及对应的x值呢?
答案:
fx=a*b=根号2sin(π/4+2x)-2cos2x
代入x=-π/4
fx=根号2sin(π/4+2*-π/4)-2cos2*-π/4=根号2sin(-π/4)-2cos-π/2=根号2sin(-π/4)=-1
时间:2022-12-24 15:49:22
已知向量a=(根号2,-2),b=(sin(π/4+2x),cos2x)(x属于R).设函数fx=a*b,求f(-π/4)的值那f(x)的最大值及对应的x值呢?
fx=a*b=根号2sin(π/4+2x)-2cos2x
代入x=-π/4
fx=根号2sin(π/4+2*-π/4)-2cos2*-π/4=根号2sin(-π/4)-2cos-π/2=根号2sin(-π/4)=-1